Human Evolution On Trial By Terry Toohill

“Human Evolution On Trial – A Case For The Defence" - Part 1 - Terry Toohill

2009-06-20T18:00:00.000+02:00

A Case For The Defence

Following private correspondence with author Terry Toohill, I've agreed to serialise his book “Human Evolution On Trial – A Case For The Defence" here at Remote Central, in the hope that not only will readers be interested to read what he has to say, but will also be prompted to add comments of their own, on what is a suitably detailed and well-researched set of chapters charting the author's take on what he also refers to as “From Apes Until today – A Case In Defence Of Human Evolution”.

I have been advised by Terry that the text is subject to copyright, as it has been placed in the Alexander Turnbull Library of New Zealand, and although I don't have details at the moment, copies may be available for purchase from the author. But for the time being, it's free to read here, so I hope readers find this a worthwhile and thought-provoking book, further instalments of which are scheduled to appear on this blog over the coming weeks.

I should also add as the usual disclaimer that the views and opinions contained therein are solely those of the author, and that he alone is responsible for the text and the details it contains, as he is the sole author - I hope that covers it.

So without further ado, here's an introduction from Terry Toohill, and my thanks to him for allowing his work to be published here at remote central.

"This extract is from partway through an account I have compiled on our evolution. My basic theme is that our cultural beliefs always influence how we interpret all phenomena. Because Judeo-Christian beliefs have been with us so long they have fundamentally influenced how we view the world. This has hampered an understanding of our origin as a species. I show that when we eliminate a biblical perspective any problems in our complete understanding of evolution disappear. On the other hand once we understand our evolution we easily see the history that lies behind stories in the Old Testament. I have divided the account into five parts.

In Part I, “Beginning - The Present”, I explain how genes work. I show how, in practice, populations or whole species can be simply regarded as a collection of genes in various proportions. I point out we could even say that each individual gene travels through a population on its own independent wave.

In Part II “Migration – The Past” I use what we know of New Zealand’s history and prehistory to show how recent human evolution provides evidence in support of the idea.

In Part III, “Biological Rules - Knowledge” I start with the short summary of the history of the earth presented here. I next look at the development of geology and then the complex question of what is a species. I show that any definition we attempt is inadequate. I then return to how biological evolution works.

Part IV “Wandering – Becoming Human” starts with our ape ancestors. I then look at the progressive development of Stone Age technology. I show that in some ways we can regard technology as evolving in a similar way to organic evolution; diversification, then hybridising followed by selection. Remaining chapters in this part follow and explain our ancestors’ biological development through various named species from Homo erectus to Neanderthals and modern humans. I argue that the ready acceptance of a mtEve single ancestor derives primarily from the influence of our Judeo-Christian background.

In Part V, I simply follow the course of modern human evolution until written records are able to tell us the historical situation in each region. I show all our culture, our knowledge, our beliefs and our skills are the result of a similar mixing, or “interbreeding”, followed by selection or culling. As a last point I compare human migration through islands in the Mediterranean Sea to that through islands in the Pacific Ocean. Finally I use my ideas to explain many stories in the Old Testament.

Preface - A Brief History of the World

Time

History needs dates and so I had better first provide a framework for all the evidence. To understand the lengths of time involved for various events during the earth’s history try this summary. It is an exponential time scale. There is a condensed version in the form of a chart starting a few pages ahead and I’m sure you’ll find it useful to refer to it when necessary. But first of all I’ll explain it.

The most recent events are at the top, or beginning of the chart, as they are in geological strata or layers. The older, or lower, layers are compressed, also as they are in geological strata. To read it in the order things happened you have to start at the bottom, or far end of the chart, but you can start anywhere. As you move back in time, or down the list, each division covers the same length of time as everything before it (or above it). As you move up the column towards the present each division halves the time between then and today. The chart has the advantage of being close to how we actually view time because as Gohau (1991) writes “every history favors the present over the past, if only because of the unequal amount of data available for the two”. I have juggled the figures a little in places to produce more significant dates but it still basically doubles all the way.

To make it relevant for humans I’ll start with a human generation of twenty-five years and keep doubling the time.

For convenience we’ll begin at 2000 AD. Twenty-five years takes us back to 1975. Fifty years ago it was 1950, soon after the end of the Second World War. Double it again and we are back 100 years, the beginning of the twentieth century, and so on.

Doubled again takes us back to 1800 AD when we each have over two hundred and fifty ancestors in our individual pedigrees. The steam engine had just come into general use (Fyrth and Goldsmith 1965) and so we could use this date to mark the beginning of the Industrial Revolution and the beginning of geology.

Double again to four hundred years ago and we are about the time of the death of Queen Elizabeth I of England (March 1603). We are well into the time of European exploration, exploitation and expansion around the world and the beginning of the latest round of extinctions. We are nearing the time of a million ancestors each. The invention of both the telescope and the microscope around this time meant science could begin. Both Lucilio Vanini and Giordano Bruno were burnt at the stake for their beliefs. Archbishop Ussher calculated the earth had been created in 4004 BC, near enough to 6400 years ago.

Eight hundred years takes us back to just 1200 AD though. There is no doubt Maori had become well established in New Zealand by this time. The Crusades were well under way and Genghis Khan took control of the Mongols.

Sixteen hundred years ago marks the withdrawal of the Roman Empire from much of Western Europe, although an argument can be made that “The West” is a continuation of it. The Anglo-Saxon movement into England coincided with the temporary disruption of the Roman Empire in Britain. Human expansion beyond Samoa into Eastern Polynesia was well underway.

Double 1600 years to 3200 years ago (1200 BC) and people using Lapita pottery were about to reach Tonga and Samoa. We are also at about the time of Ramesses III of Egypt and the migration of the Sea People through the Mediterranean Islands, what we might call the last point of the human star. It may also be the time of any kingdom of Israel in the Middle East under David and Solomon although not all people regard all these events as being contemporary.

Double again to 6400 years ago (4400 BC) and we are at about the beginning of cities in the Tigris and Euphrates River valleys (Mesopotamia) in what is now Iraq. Much older towns have been found just outside the region though (for example at Jericho). The keeping of records through the use of writing probably began around this time. And Archbishop Ussher believed the earth had been created then. People in the Balkans were working copper (James 1991) and the Austronesian-speaking people began their expansion from Taiwan. People with the Linear Pottery or Danubian culture were moving into Europe.

If we double again we reach 12,800 years ago but we’ll round the date to 12,500. We are near the end of the ice age and the beginning of human movement into the extreme end of the Northwest European point of the human star and into the American sub-point. The first steps towards farming were probably also made at this time both in the Middle East (the Fertile Crescent) and in Southeast Asia (the Hoabinhian culture).

Double the time again and we have 25,000 years ago, about the time people with the “Gravettian” stone-age culture moved into Western Europe from east of the Carpathian Mountains, from Southern Russia. Modern humans finally replaced the Neanderthals, probably at least partly through the formation of hybrids. The Gravettian people probably used the same route as the Corded Ware people were to take 18,000 years later. African and European cattle separated at about this time.

About 50,000 years ago humans known as Cro-Magnon started moving into Europe, most likely from the southeast via Turkey and Greece. They introduced the “Aurignacian” technology. At the opposite side of the human star people were able to move into Australia for the first time.

Fully modern humans, or Homo sapiens, are said to have left Africa by the time we double again to 100,000 years ago. They may have been held up in the Middle East because Neanderthals (Homo neanderthalensis) keep popping up there over the next 50,000 years.

200,000 years ago we have Homo heidelbergensis in Europe (the first fossils of it were found near Heidelberg). Neanderthals and modern humans both presumably developed from this species (possibly with some input from earlier Homo erectus). Neanderthals’ culture is called “Mousterian” and involved the “Levallois” technique of working stone.

The Levallois developed some time between 200,000 and 400,000 thousand years ago and 400,000 years ago is about when Homo heidelbergensis developed, presumably from some sort of Homo erectus.

By 800,000 years ago the species Homo erectus had probably reached the geographical extremes of their range. It was not until four divisions more recently that humans were able to expand further, into Australia. We’ll return to this summary in a while but now is a convenient place for us to have a rest and for me to show you the chart.

A short history of the Earth.

0: 2000 AD The New Millennium

25: One generation, back to 1975. I left the Manawatu and returned to Northland

50: End of Second World War (roughly). I was born (a little less roughly)

100: Beginning of the twentieth century. Humans found they could fly after all

200: The Industrial Revolution began and Europeans started moving into Australia and New Zealand

400: Time of Queen Elizabeth I. Europeans off learning about the world. Bruno executed

800: Maori in New Zealand by this time. Inquisition established

1600: Decline of Roman Empire, Anglo-Saxons into England

3200: About the time of Rameses III of Egypt and the Kingdom of Israel. Lapita pottery people to Tonga and Samoa.

6400: Cities developing in the Middle East and possibly Egypt. Linear pottery-bearing and Austronesian-speaking people begin their expansion.

12,500: End of ice age. Beginning of farming and Hoabinhian culture. Humans able to enter what I call the American subpoint of the human star

25,000: In Europe the Gravettian stone tool culture moved in from the northeast

50,000: Aurignacian stone tool culture into Europe from the southeast. (Cro-Magnon man). First humans into Australia

100,000: Human expansion out of Africa. They and Neanderthals alternate in the Middle East for half the time between today and then

200,000: Mousterian (Neanderthal) stone culture and evidence of fire in Europe

400,000: Evolution of Heidelberg Man and Levallois stone working

800,000: Homo erectus reaches maximum distribution around the earth

1.875 million: Evolution of Homo erectus in Africa and Asia. Ice ages well established

3.75 million: Good fossil evidence for Australopithecus (Lucy)

7.5 million: Roughly time of split between humans, chimps and gorillas. Three-toed horses out of America

15 million: Africa became jammed into Asia and Europe. Ancestors of modern apes able to move between these continents

30 million: Mid-Oligocene geological epoch. Apes separated from monkeys during this period

65 million: End of the Cretaceous geological period and the dinosaurs. Continents started splitting and age of mammals began. Monkeys already developing

130 million: Beginning of Cretaceous (end of the Jurassic period). The Cretaceous fills half the time between today and then

260 million: Beginning of the Permian geological period. Most of the oldest rocks in New Zealand were laid down over the period from the Permian to the end of the Jurassic. Again this took up half the time between today and then

520 million: End of the Cambrian geological period. The first mass extinctions we are aware of

1040 million: Possibly an ice age

2080 million: Primitive life on Earth

4160 million: Round about the beginning of the Earth

Now to carry on:

Double again to 1.6 million years ago and we have Homo erectus beginning their expansion. We should probably call them the first humans. The latest series of ice ages had started a little before this time. There have been up to twenty cycles of extreme cold followed by periods as warm as or warmer than today. The climate had actually already been steadily cooling for more than 30 million years before this though. The period of the ice ages is known as the “Pleistocene geological epoch”. The beginning of the Pleistocene, about two million years ago, also marks the end of the Tertiary and the beginning of the Quaternary geological period.

Homo erectus evolved more than 1.7 million years ago but I’ll use 1.875 million years. When that is doubled it comes up 3.75 million years ago. From about this date there is good fossil evidence in Africa for presumed Homo erectus and human ancestors in the form of “Lucy” and other Australopithecus species (Johanson and Edey 1982). Some genetic evidence has been interpreted as showing humans, chimpanzees and gorillas may have finally separated as recently as this date (Gribbin and Cherfas 2001). Various species of Equus and camels moved out of North America also about this time.

Doubled again is 7.5 million years and three-toed horses moved out of North America. This is also about the earliest time given for the split between chimpanzees and humans, although gorillas may have separated even earlier. A fossil of this age that could well lie on the line to humans has recently been found in Chad (Lemonick and Dorfman 2002).

Fifteen million years ago, in the middle of the Miocene geological epoch, Africa became jammed up against Asia and Europe (Attenborough 1987). This allowed the ancestors of the modern (or brachiating) apes to move between Africa and Asia (brachiating is the ability to swing or hang from branches by your arms). In fact it is possible the ancestors of the present African apes (including humans) actually moved into Africa from Asia (Gribbin and Cherfas 2001). The gibbons may have separated from the rest of the ape line as early as fifteen million years ago. They have become particularly effective brachiators. The orangutan separated eight to ten million years ago.

Double again and we are in the middle of the Oligocene geological epoch, at 30 million years ago. Three-toed horses appeared in North America and the ancestors of deer and giraffes separated from other ruminants during this period. Camels and llamas had already parted from them. We can use evidence from these and many other species to prove what a friend has called the wave theory of genetic, cultural and technological evolution. This theory is able to help us interpret the evidence for our evolution from apes until today. So do we need to go further back if we are concerned just with this? But I’m on a roll and for now I’ll just keep doubling the time until I reach the beginning of the earth.

Apes seem to have separated from monkeys during this period. Apes diverged into many species most of which (apart from some of the later brachiating ones) eventually became extinct. During the Oligocene the continents were at their lowest altitude, having been eroded down since well back in the Cretaceous period. The climate was very warm and seas were at their highest. From the Oligocene until the present the continents start bumping into each other again. Mountains rise and the sea is able to sink into deeper ocean basins. This period also marks the beginning of the climate cooling that led ultimately to the latest series of ice ages. The immediate cause of the cooling was probably the opening of the gap between Australia and Antarctica. This allowed the southern circum-polar current to develop (Stevens 1985).

Double again and we have 60 million years but we’ll make it 65 million years, which marks the end of the Cretaceous geological period and the beginning of the Tertiary geological period. It also marks the extinction of the dinosaurs and beginning of the age of mammals. Some people believe the dinosaurs didn’t actually become extinct. Small versions that had evolved feathers, probably to keep warm, evolved into birds.

The Cretaceous itself in fact lasted about 65 million years and so the Cretaceous began 130 million years ago. This earlier date marks the end of the Jurassic period and the beginning of another breakup of continents. Virtually all the sea floor on earth is younger than this date and most of it is younger than half this age (Jones 2000). The lowering of mountain ranges by erosion and the gradual filling of sea floor with the sediment during the sixty-five million years of the Cretaceous eventually had the effect of raising sea levels and partially flooding the continents. The gradual isolation and size reduction of the continents during the Cretaceous period and consequent climate and environmental change may have had as much to do with the eventual extinction of the dinosaurs outside North America as did the asteroid collision. Dinosaur extinction was actually very protracted; at least hundreds of thousands of years (Jones 2000). And possibly millions but humans like the idea of catastrophes. In fact many people hope the world is going to end soon.

The massive eruption of volcanoes on the Deccan plateau of India near the end of the Cretaceous would have contributed to the dinosaur extinction and could be partly responsible for the layer of heavy metals found in sediments from 65 million years ago throughout the world. Although Richard Corfield (2001) does mention this possibility he seems to suggest the idea has been rejected largely because of political and funding considerations. He actually offers no evidence to dispute it. Most mass extinctions have coincided with large volcanic eruptions though (Wade 2001).

The ancestors of monkeys and lemurs had separated from other mammals at some time during the Cretaceous, probably along with the development of flowering plants, especially trees (Tudge 1996). Flowering plants appeared in the mid-Cretaceous and the evolution of grass may have been the final straw, so to speak, for the dinosaurs. Grasses didn’t actually reach their major expansion until more recently though (at the beginning of the Miocene epoch about 25 million years ago) and ruminants or cud-chewing animals seem to have started developing a little before that time. The expansion of grassland was also responsible for the development of horses.

Double the time again and we get 260 million, the beginning of the Permian period. The Permian is actually in the Paleozoic geological era but the Paleozoic ends with the end of the Permian, about 235 million years ago. Great volcanic eruptions and a series of ice ages similar to the ones the earth has just been through mark the end of the Permian. But the continents were in much different positions than they are today. The time also marks easily the greatest mass extinction event we are aware of. It makes the extinction event at the end of the Cretaceous (which included the extinction of the dinosaurs) look relatively minor, about number five on a list of severity.

Double again: 520 million is the end of the Cambrian period, marked by the extinction of much of the variety of life that had developed by that time. The Cambrian began about 570 million years ago with a huge explosion of life forms (Corfield 2001). Supporters of the Intelligent Design theory of evolution apparently believe this happened through a creation (Wells 2000 and Dembski and Kushiner 2001). Anyway whether it happened by creation or not is irrelevant to whether or not we evolved from apes.

1040 million years is in the Precambrian era and someone else can look for significance in that date but some evidence suggests complex life began about then (Wade 2001). Intelligent Design supporters presumably would say through another creation event. Until James Hutton’s time most geologists used the idea there have been several “creations” to explain the fact that throughout the world rocks of the same age have similar collections of fossils, many of them not present in more recent levels (Gohau 1991). Most early geologists believed each group of earlier life had been destroyed by catastrophes. There had been a series of beginnings. Others began to see a basic thread that indicated life had changed or evolved through the history of the earth.

We can see that the same old argument carries on in the conflict between creationists and evolutionists. The term creationist covers a huge variety of beliefs though. Some of them even accept evolution has occurred but that it has happened by design (Wells 2000 and Dembski and Kushiner 2001).

The preference of any individual to accept either gradual or sudden change (or even no change at all) as an explanation for the development of life on earth depends very much on what has been, or is, important in their own life. It is difficult for us to imagine the world has ever changed more than it has over our own lifetime. We also carry many mythconceptions from our childhood. I believe the conflict between a belief in gradual or sudden change is actually at the core of the debate between the “spread origin” and “single origin” theories of human evolution. You will be able to decide for yourself which is the most likely theory as we examine the evidence.

2080 million years may be significant (perhaps the beginning of life itself) and the earth is said to have begun a little more than 4160 million years ago."

References

Attenborough, David (1987) The First Eden. Guild, London.

Corfield, Richard (2001) Architects of Eternity. (UK/US) Headline Book Publishing, London.

Dembski, William and Kushiner, James (2001) Signs of Intelligence. Brazos Press, USA.

Fyrth, H. J. and Goldsmith, M. (1965) Science History and Technology Book 1. Cassell, London.

Gohau, Gabriel (1991) A History of Geology. Rutgers University Press, New Brunswick, USA.

Gribbin, John and Cherfas, Jeremy (2001) The First Chimpanzee. Penguin Books, England

James, Peter (1991) Centuries of Darkness. Jonathan Cape, London.

Johanson, Donald and Edey, Maitland (1982) Lucy. Warner Books, New York.

Jones, Steve (2000) Almost Like a Whale. (UK/US) Anchor, London.

Lemonick, Michael and Dorfman, Andrea (2002) Father of us All? Time, July 22nd.

Stevens, Graeme (1985) Lands In Collision. Science Information publishing Centre, Wellington

Tudge, Colin (1996) The Time Before History. (UK/US) Scribner, New York.

Wade, Nicholas ed. (2001) The New York Times Book of Fossils and Evolution. The Lyon Press, New York.

Wells, Jonathan (2000) Icons of Evolution. Regnery Publishing, USA.

Human Evolution on Trial – Contents/ Finding Your Way Around

2009-06-20T17:55:00.000+02:00

Human Evolution on Trial – Contents/Finding Your Way Around

This contents list will help anybody interested understand the thread of logic that runs through this case. Not all chapters are up yet but I don't think there's any hurry. I'm more than happy to argue with anyone who wishes to. And, of course, I'm more than happy to hear from you if you're able to improve the defence case, or even just agree with it.

Human Evolution on Trial - 'Human Star - The Last Point'

And scroll down to “Summing Up”.

Part I – Beginning

Conception Order, The Prosecution, The Defence, Me, You, The Chinese Drover’s Very Clever Dog

Chromosomes and DNA Y-chromosome, Nuclear DNA, Dominant and Recessive Genes, Mitochondrial DNA

The Human Star Geography, A Map, The White Man, A Cline, Altitude

Pedigrees Ancestry, Populations, Selection

Mythconceptions Oral History, Science, Ancient Myths, Modern Myths

Part II - Migration

Change New Zealand, Destruction, Tribes, Galapagos Finches, Variation Through Space, Variation Through Time, European Migration

Hybrid Vigour and Inbreeding Hybrid Vigour, Inbreeding, Wave Theory of Evolution, Survival

Eastern Polynesia Polynesian Languages, Islands, Marginal Polynesia, Easter Island

Polynesian Origins Language Families, Genes, Societies, Taiwan, Japan, Na-Dene

Pacific Population The Canoe, Hoabinhian, Mixing, Lapita, The Sail

Indo-Europeans Indo-European Languages, The Chariot, Mingling, Slavic, Celtic, History

Part III - Knowledge

Time A Short History of the Earth

Long Ago Geology, Continental Drift, The Horse

Species Kinds, Difference, Labels, Ecology

Evolution Purpose? Ecological Speciation, Hybrids, Punctuated Equilibrium, Geographic Speciation, Ruminants, The Human Influence

Extinctions What Have We Done? How Did We Do It? The Results

Part IV - Wandering

The First Point Origin, Australopithecus, Homo habilis, Caucasus Population

Technology Lower Paleolithic, Middle Paleolithic, Upper Paleoloithic, Progress

First Humans Homo erectus, Expansion, Subspecies?

Species or Not Homo heidelbergensis, East Asian Point, Australian Point, Both of Them

Neanderthals et al Two From One, Climate, Aurignacian and Mousterian, Superiority

MtEve The Trees, The Branches, Interpretation, Mungo Man

Part V - Conquest

Out of Africa The Middle East, Cro-Magnon, Genes Again, Asia

Into Australia The Dreamtime, Wallace’s Line, Kow Swamp, Indo-Pacific and Pama-Nyungan, Explanation, More Evidence

Culture Languages, Families, Europe, Religion, Evolution of a Religion, Wave Theory of Knowledge

North to Alaska The Ice Age, The Gravettian, The First Americans, Genetic Evidence, Later Migrations, Eurasiatic, Neighbours

The Last Point Islands Again, Pottery, The Western End, The Eastern End, Dating, Gene Flow, The Sea People, Phoenician Friends, Summing Up

See next :: Human Evolution On Trial - Conception

Human Evolution on Trial - 'Conception'

2009-06-20T17:50:00.000+02:00

Human Evolution on Trial - Conception

I need first of all to explain how I have set out the evidence I have gathered [Order], and why. Next we’ll look at some debates over how evolution happens, or, according to some people doesn’t happen at all [The Prosecution]. I’ll then introduce myself to you and examine how we come to know what we think we know.

Our individual conception of the universe evolves through the input of conceptions we are exposed to as we grow up. New ideas always trickle gradually to various groups of individuals though. In the early 1600s Galileo completely upset our collective conception. He proved the earth moves around the sun. But a survey in France nearly four hundred years later showed that one third of the people there still believed the sun moves around the earth (Gohau 1991). Presumably some still believed the earth is flat.

In spite of the huge advances in the explanation of human origin made over the last 150 years a huge number of different theories still circulate about how we humans have arrived on earth. Most of these theories involve distorting, or selectively ignoring (perhaps unconsciously), relevant evidence. Many fossils have been discovered and forensic science has helped immensely in examining and interpreting all this evidence. A great deal of work has also been done on the ways genes work and how they, technology, culture and languages move, and change, through time and space. But in many parts of the world there has recently been an increase in religious extremism and growing unwillingness to accept the idea that we humans are basically a kind of ape.

Perhaps the one idea we can assume is true is that debate always improves our own ideas. The process produces a sort of hybrid vigour. Any opposition also clarifies our own ideas and theories. It focuses our point of view. To provide a framework for my explanation of the evidence I have decided to present this story as an argument against the evolution-deniers among us. I will use the idea that a defendant, Human Evolution, is on trial. Of course this trial is really about much more than just that. For example, cultural beliefs have always been used to justify both economic exploitation and the acts of terrorism committed in response. The trial is really about the attitude we have to our surroundings and the way we treat our planet and its inhabitants.

As we wind our way through the evidence I will imagine you, the reader, to be a member of the jury. But at various times you will probably consider yourself to be either a member of the defence or part of the prosecution. The defence case will explain exactly how, in the right circumstances, collections of genes and even individual genes spread through populations or into new regions. One of my friends has called this the wave theory of genetic, cultural and technological evolution. The jury will see that this theory totally explains our evolution from the apes until today. In fact it explains the evolution of all species at all times. Along with many other things. Even our collective and individual ideas and beliefs evolve in much the same way. I’ll begin the defence case once I’ve completed this introductory chapter. Much later, when I have explained exactly how the wave theory works, it will be sensible for us to follow our more recent history from this perspective.

The members of the prosecution are those in society who, for various reasons, claim the main outline of our evolution is not proven beyond reasonable doubt. At this point I would point out to the jury that members of the prosecution cannot actually offer any evidence, apart from ancient beliefs, to support a detailed, and certainly not a unified, alternative explanation for how, when, where and why we arrived on earth. Luckily we have a right as citizens in a democracy to question everybody’s motives. Although not all members of the prosecution belong to powerful or influential elements in society many of them do. Perhaps economics comes into it. Perhaps they hope their God is going to come back soon and, like their parents used to do, clean up any mess they make.

Order

Unfortunately I haven’t always found it possible to present all the evidence that supports a particular conclusion in its logical place. For example evidence that explains the human migration “North to Alaska” and then into the Americas also supports many conclusions I offer long before we reach that point. However for various reasons it is most convenient to present the particular evidence towards the end of my story. I’m sure the jury will still follow the various threads and not find this to be a problem though.

I admit that some items of the evidence may be subject to several interpretations. But surely the jury will be aware of the fact that it is usually possible to prove anything by selectively ignoring some, or even a great deal, of relevant evidence. Politicians and other powerful and influential people use the technique expertly. It’s usually successful. We cannot all know all the evidence. Although I realise many members of the jury will already know a great deal of the information presented, I’m sure you will all enjoy having it gathered together in one place and at your fingertips. Others of you will know less about the subject and I hope you find it as fascinating as we members of the defence do. Besides there is a difference between blindly accepting that we evolved from apes, and having the knowledge of how it happened. And it helps us understand events today.

The evidence I invite the jury to consider will concern the past. You might be tempted to say our ancient past is not important. But I would like to point out that our conception of the past and our beliefs about it influence our actions in the present. And of course these actions, in turn, will influence our future. I would suggest, though, in order to understand the past, let alone the future, we need first to understand the present.

In Part I - “Beginning” I will therefore first of all examine what we know about you, the individual person, and I explain how genes work. I then expand the view to include your progressively more distant relations, neighbours and friends. Even to the distribution of different human types around the earth today (“The Human Star” [A Map]). Although the defendant is Human Evolution along the way I will call on evidence from other creatures, and even from plants, to explain various aspects.

In Part II - “Migration” I use this evidence from the present to move slowly back into the past. New Zealand is one of the most recently settled regions on earth. To explain how the wave theory of evolution works I therefore use what we understand of the evolution and eventual mixing of the two main groups of people, Pakeha and Polynesian, in my home country.

In Part III - “Knowledge” I widen the perspective through both time and space. I show that these processes at work in New Zealand also explain all the fossil and genetic evidence for the evolution of all the various kinds of animals, birds and plants, along with the patterns of their distribution around the earth.

In Part IV - “Wandering” and Part V - “Conquest” it’s time to turn around, and start at the beginning. The jury will then be able to follow, examine and understand the meandering strands of our species’ evolution since our separation from the other apes, “The First Point” [Origin].

This will leave us with the problem of where to finish.

It will be least complicated to finish when we arrive at history. By definition history was not possible until people were able to record their version of events by writing them down (“Mythconceptions” [Oral History]). Writing seems to have begun near the eastern end of the Mediterranean Sea (“The Last Point” [The Eastern End]). Probably for that reason many political, philosophical and religious ideas through much of the world have their origin in the interaction of culture in and around that region. History begins there. In Part V the wave theory will help the defence explain the origin and perspective of these histories. For example the jury will see that the Old Testament of the Bible records such events as the Hyksos migration from Egypt and the migration of the Sea People. And many islands in the Mediterranean were, like the Pacific Islands, among the last places humans occupied. For these reasons the defence will call the Mediterranean Islands “The Last Point”.

The jury will also find that the history of the Mediterranean’s occupation will actually bring us around in a big circle. I’m confident that by the time you have completed that circle you will accept the defence’s interpretation of the evidence. No doubt various members of the prosecution will still disagree with many of these interpretations, but I’m afraid they’ll have to tell you themselves which ones they individually disagree with.

You will be able to see the layout in more detail, and go directly to most sections, from: 'Contents - Finding Your Way Around'

Because it has been so important in human history the defence will examine the evolution of culture at times. And technology. The distribution of various technologies and cultures reveals a great deal about human migration, expansion and evolution. This evidence will help the defence explain the wave theory. Of course the jury will realise it’s possible for a single person to spread culture, especially technology or an idea, and a genetic mutation must first arise in a single individual. But technology and many aspects of culture have always travelled faster and usually further than genes.

Although technology is really a part of culture the defence case will look at technology separately. Technology usually leaves evidence in the archaeological record whereas most other elements of culture don’t show up so well. It is also almost certain that in the very early stages of our existence technology was actually transmitted without language. Chimpanzees use basic tools for example.

The defence defines culture as being the things we have to learn that make us part of our social group. In their natural state most animals have to learn survival techniques off their older relations and in many ways this can be thought of as being culture. The study of wild chimpanzee and gorilla societies is especially interesting for this aspect of our evolution (see for example Fossey 1983, and Goodall 1990). But within the concept of culture the defence includes here only those things we learn through language: knowledge, beliefs, music, art, games, rituals, traditions, ideas, etc. (and obviously the language we speak is part of our culture). In fact the jury will see that this whole case is the result of a cultural exchange of knowledge accumulated by a huge number of humans ranging from friends and neighbours to people I have never met, including many who died long before I was born. You can probably already accept that culture evolves. In fact the defence will argue that technology and culture even obey much the same biological rules that species do. No doubt a general acceptance of the wave theory of genetic, cultural and technological evolution would ultimately lead to a change in culture.

The Prosecution

The prosecution are those of us who, perhaps to make money off others of us, maintain the defendant doesn’t exist. They constantly chant that there can be no absolute proof of Human Evolution. Of course it is very seldom evidence provides “absolute proof” of anything. It can only suggest probabilities. The defence would remind the jury that there is actually a totally overwhelming lack of proof for any theories the prosecution offers for our arrival on earth. The prosecution’s proof of their own beliefs simply involves pointing at particular ancient books. The only evidence they offer is to point at the current gaps in our knowledge. The defence suggests that the prosecution’s case relies totally on the theory of negativity: life couldn’t have evolved because it wouldn’t display the complexity it does if it hadn’t been created. Follow that?

The defence asks the jury not to be distracted into considering any other cases evolution-deniers have brought. These include “The Origin of Life” and “The Origin of the Universe”. We’ll look briefly at them in “Time” but these cases are best heard separately. And we should stick with what we can easily prove beyond reasonable doubt, Human Evolution from apes until today.

Besides, even many supporters of the modern idea of Intelligent Design, for example, would not dispute either the pattern or the time frame for Human Evolution suggested by the evidence the defence will present. They simply believe their God has had a purpose in guiding this evolution, from ape right up until today, especially during the historical events covered in “The Last Point”. A supporter of Intelligent Design (Wells 2000) concedes: “Obviously, the human species has a history. Many fossils have been found that appear to be genuine, and many of them have some features that are ape-like and some that are human-like”. The defence will offer these fossils as evidence later during the trial.

Of course even a very casual look at the evidence shows us at least some evolution has occurred, even if only a little bit. If we accept for now the widespread belief that humans descend from just one couple the only possible explanation for the variation we see in humans today is some form of evolution. A closer look at the evidence shows us that different species can actually be classified into groups that seem to be related. Members of the prosecution often explain this by claiming that various “kinds” were created, which they admit then evolved into these groups of species. But they are extraordinarily secretive as to exactly what kinds were created, and when.

The Defence

Not surprisingly the prosecution prefers drawing attention to disagreements among the defence rather than pointing at their own much more extreme differences. Members of the defence all agree that humans have a close genetic relationship with the apes of Africa: the chimpanzee and gorilla, and all three have evolved from a common ancestor. Several interpretations are possible for the evidence surrounding this common ancestor, though, and we’ll return to this when we reach “The First Point”. By then we’ll be able to use the wave theory of genetic, cultural and technological evolution to interpret the evidence.

The main disagreement within the defence concerns two conflicting theories concerning the pattern of our evolution.

We could call the first of these the “single origin” theory. This states modern humans evolved in Africa one or two hundred thousand years ago, moved out of that continent at some time and replaced all earlier human types. Genetic evidence showing all humans alive today share a male and a female ancestor supports the theory. There is also some fossil and other genetic evidence for the single origin theory. Supporters believe this is how evolution usually works; a small group expands and takes over. The theory has the advantage that it coincides, to some extent, with widely held cultural beliefs. It may even derive from them. In fact the two ancestors are often referred to as “Y-chromosome Adam” and “mtEve”.

The “spread origin” theory states humans have been what can be defined as a single species for much more than just the last 200,000 years. Our evolution has been by change and gene flow, the continuous separation and intermingling of human populations. The theory’s supporters suggest the evidence for mtEve represents something far more complicated than what has generally been promoted to the public. They believe that no species, including the human species, descends from a single individual, a single couple or even a single small group. But people always demand simple answers to complex questions.

I must stress that this is my personal presentation. I’ll point out when it is specifically my interpretation but at other times I assure the jury that the interpretation offered is widely accepted by scientists such as anthropologists, zoologists, botanists, ecologists, geneticists, geologists, archaeologists, palaeontologists and linguists. Most of them would agree with most of my explanations but the jury will see that at times I offer an interpretation that scientists from one side or the other of any debate might not agree with.

People who specialise in the various sciences can perhaps become too involved in their own particular field to be able to look objectively at all the evidence. My training is in the more general field of agriculture. Agriculture requires knowledge of animal behaviour, practical animal and plant breeding and ecology, as well as an awareness of climate fluctuations, geology and an interest in nature generally. In fact farmers are trying to influence evolution every time they decide which animals to breed from and what weeds to destroy. They actually make better decisions if they are aware of this.

I have brothers who have been dairy farmers and because our parents were farmers I had the good fortune to be brought up on one. Farmers are all involved with the practical side of genetics. They usually notice that if they form a hybrid, or a cross between two different animal breeds, the individual or line of individuals they finish up with has a mix of characteristics from each original parent breed. In fact many characteristics are sort of halfway between the two. I’m confident that after examining all the evidence available you will accept that the evidence reveals at least some influence of the spread origin theory. The single origin theory requires selectively ignoring some of the evidence.

Modern developments in agriculture, especially in plant and animal breeding, provide us with a great deal of information about how this sort of evolution works. But people in the industry are often reluctant to use the information to support the defendant. It might involve them in controversy and perhaps alienate some of their clients. Many probably also lack time to find all the information.

I have been a musician for most of my life and through my interest in various types of world music, I have noticed that as the many tunes and musical styles move around the world they combine and alter, they change. In other words music evolves. Music is a part of our group’s culture and reinforces the sense of belonging to that culture. Historically the role of a musician in many societies has been to recite the genealogies, the history and the mythology of people in that society. Unfortunately I haven’t yet been able to put my story to music. However I do use several phrases many times and you may call these choruses if you wish. Of course you can choose for yourself the music you use as accompaniment while you study the evidence.

You

You will find that, like most things, the whole idea is stunningly simple to understand once you grasp it. Unfortunately, also like most things, it is difficult to explain simply otherwise it would be already totally accepted. This is not a straightforward story. Our family history is the result of diversification, amalgamation and interaction with other humans and other species (plants, diseases, animals etc.), and even changes in the earth itself. Because we can be sure the prosecution will very quickly pounce on the slightest gap in the evidence the jury will find this case at times becomes quite detailed and contains some technical terms. Fortunately it’s not necessary for you to remember the details in order to follow the story. You may even be able to follow it simply by looking at the maps, or by starting at “The Last Point”. Once you understand it you will be able to explain it to others.

The defence has tried to keep the number of “Witnesses Called” (in the form of references) to a manageable level. The reference given is the one members of the jury should easily find through a local library or on the Internet, but it is not necessarily the primary reference. If you are interested in following a particular subject up you should have no difficulty finding the primary references through the ones given.

The prosecution often claims there has been a huge conspiracy. They suggest that we, the defence, have somehow persuaded all these witnesses to make up evidence in support of the defendant. You will come to realise that the evidence many witnesses offer was not originally directly connected at all to the defendant. Most of the witnesses didn’t actually set out to provide evidence in support of the defendant in any way. In fact many may still not be aware of the significance of their evidence.

A quick word about dates. Most dates used in this case have “about” in front of them. Again the prosecution seems to have trouble with this. They expect the defence to be able to say that, for example, the Polynesians first arrived in Hawai‘i at 4.25 p.m. on the 23^rd of August 432 AD. Surely “about 400 AD” is near enough. Modern dating methods such as carbon dating are always presented with a margin of error but this doesn’t mean they are therefore totally wrong and can be dismissed. Political polls also have a margin of error. It’s mainly the politicians who are shown to be losing who dismiss the polls’ general accuracy though. “About 30,000 years ago” is obviously much longer than “about 3000 years ago”. Interestingly you will find that members of the prosecution who criticise the lack of precise dates for the various stages of human development seldom provide any real evidence for accurate dates to support their own beliefs.

The Chinese Drover’s Very Clever Dog

There is one last point to make before we get this trial properly under way. We can quite easily come to the wrong conclusion; the conceptions we have accumulated encourage us to juggle the evidence to make it fit our beliefs. These beliefs are a product of how we are brought up. And we usually assume our own beliefs are superior to any others. They are the ones we know best.

We are all products of our cultural environment (Howe 2003). We are all completely unaware of what shared beliefs and personal biases we bring to our understanding of the world and how it works. Our conception of the universe is slowly built up through our lifetime, and the beliefs we form at each stage of our life as we grow up, especially those formed during early childhood, are very difficult for us to discard. In fact we can understand new information only by relating it to our pre-existing beliefs, or what the defence will later call our “Mythconceptions”. The defence suggests that widespread collective assumptions, preconceptions, and prejudices may have influenced generally accepted interpretations of the evidence concerning the defendant. Or even influenced the choice of what evidence has actually been either examined or ignored. Assumptions, preconceptions and prejudices certainly influence our individual conceptions.

My father grew up during the 1920s in the small country town of Eketahuna. There was a Chinese drover in the area. In those days (before stock trucks) people called drovers used dogs to move cattle from place to place. When my father was quite young he told my grandfather that the Chinese drover’s dog was very clever. When asked why he replied, “He understands Chinese”. Through his own assumptions, preconceptions and prejudices my father had presumed English would be a dog’s first language. It was obviously the normal language. All the people and dogs he’d had anything to do with understood it. And none of the other dogs he’d ever seen understood Chinese. The Chinese drover’s dog may well have been very clever but the fact it understood Chinese is not relevant evidence. This is an example of how what we already accept as being true prevents us from looking at the evidence objectively, or even at all of it. This affects our conclusions.

The problem is by no means confined just to children. In fact the defence will use the expression “Chinese drover’s clever dog syndrome” as one of the choruses as the trial proceeds.

No doubt many members of the prosecution will question the defence’s comparing humans with birds, animals and plants. But surely it is the prosecution who must first provide evidence to prove to the jury exactly how, why, and in what specific ways, humans differ. The defence suggests that the idea there are two sets of biological rules, one for humans and one for the rest of nature, may be our first example of Chinese drover’s clever dog syndrome, juggling the evidence to make it fit pre-existing assumptions, preconceptions and prejudices.

See next :: Human Evolution On Trial - 'Chromosomes and DNA'

Witnesses Called

Fossey, Dian (1983) Gorillas in the Mist. Penguin, England.

Gohau, Gabriel (1991) A History of Geology. Rutgers University Press, New Brunswick, USA.

Goodall, Jane (1990) Through a Window. Houghton Mifflin Company, Boston.

Gore, Rick (2002) New Find. National Geographic, Vol. 202, No. 2, August.

Howe, K. R. (2003) The Quest for Origins. Penguin, New Zealand

Wells, Jonathan (2000) Icons of Evolution. Regnery Publishing, USA.

Human Evolution on Trial - 'Chromosomes and DNA'

2009-06-20T17:45:00.000+02:00

Human Evolution on Trial - 'Chromosomes and DNA'

Most members of the jury will have heard of genes and know they are responsible for our inherited characteristics. As you probably already know, your genes control such things as your skin, hair and eye colour, the shape and size of your face, eyes and nose, your blood group and to a large extent your general height and shape as well as many other things, such as elements of your personality (Steve Jones 2000). One of my brothers believes even the willingness, or otherwise, of individual dairy cows to come into the open side of a herringbone milking shed is inherited. Anyway it is most likely that instinctive behaviour is genetically inherited in some way. Humans have many instincts. One of them is the ability to learn a language (Ridley 2000). We’ll come back to language periodically.

Humans may have up to a hundred thousand genes although the precise figure is debated. Some say many less than half this number but, almost certainly, the complex interrelationships between genes are usually underestimated. A change in a single gene can have a huge effect. For example cultivated maize differs from its vastly different wild form in just five genes (Jobling et al 2004). The environment we are brought up in does affect the influence of our genes, and some evidence indicates it may influence the genes themselves, but we can ignore both of these possibilities for now.

Experiments have shown that genes for each of your characteristics occur in pairs, one of each pair from your mother and your father. If the two genes of a pair are different usually only one of them gives rise to your observed characteristics. This one is called the “dominant” gene. The other one remains hidden but can be passed on to any of your offspring. This gene is called “recessive”. The evidence shows that your genes are carried on your chromosomes, which are confined to the nucleus (the centre) of each cell of your body. Except for the Y-chromosome, chromosomes usually occur in pairs. In fact the jury will see that a hierarchy of pairing passes on genetic information.

Y-chromosome

Each single chromosome, of each pair, consists of a double string of DNA (deoxyribonucleic acid) mixed with proteins. DNA is actually a string of what are called nucleotides attached to a series of alternating sugars and phosphoric acid (technically the nucleotide is the combination of all three chemicals). Just four types of nucleotides are present in the chain. In DNA they are adenine, thiamine, guanine and cytosine or A, T, G and C. Each strand of DNA is a string of up to a hundred million of these four nucleotides in various sequences giving a total of about three billion for the total human genome (see for example Stringer and McKie 1996). In the paired strand of nucleotides in each chromosome the adenine in one strand is always joined by hydrogen bonds to thiamine in the other, and guanine in one is joined to cytosine in the other strand (A-T, G-C). This means that chromosomes are easily able to replicate themselves. When the double strand of DNA splits each separate strand must replicate the other strand. Therefore the two new chromosomes, or double strands of DNA, are exactly the same as the original chromosome. The defence has included drawings of dividing strands of DNA in the genetic maps presented later (see for example map 2).

The main visible aspect of the function of DNA is the form we take as a developing foetus, our general shape and what type of creature we are. However in many parts of our body throughout our life DNA continually reproduces itself. This replaces our worn out tissue. But mistakes do occur and cancers can result.

In fact mistakes in the sequence of nucleotides in the DNA are reasonably common and are called mutations. Even identical twins have a few dozen differences in their total DNA (Cavalli-Sforza 1995). Harmless mutations in your reproductive cells are passed on to your descendants. These mutations lead to variation in the genetic makeup of individuals, and ultimately of different populations. In some cases it has been possible to work out the sequence in which such mutations have occurred. We’ll come back to this soon.

Apart from reproductive (sperm and egg) cells each cell of the human body has 46 chromosomes, made up of 23 pairs. Chromosome pair 23 is either a pair of X-chromosomes or a single X and a single Y chromosome. This determines whether you are female (XX) or male (XY). This is not true for all creatures. In birds and butterflies for example it is the female that has the equivalent of the XY combination.

Reproductive cells have only one of each pair of each chromosome, i.e. for humans 23 chromosomes including either a single X or a single Y. When fertilization occurs the normal condition of pairs is restored, one of each pair from each parent. Individual chromosomes are not passed unaltered from generation to generation though. Pieces can cross between the pairs of chromosomes during the formation of the reproductive cells. Because of this, genes from each parent can be thought of as mixing sort of randomly for the next generation. Gene linkages do occur, basically because genes close together on the chromosome are less likely to be separated (Jobling et al 2004). For example the genes for blond hair and blue eyes usually go together in humans, although they do show some independence.

During the formation of reproductive cells the pair of X-chromosomes in women behaves in much the same way as all the other pairs of chromosomes do, they mix. But, because there is no corresponding part on the X-chromosome for it to join with, most of the Y-chromosome is passed virtually unchanged from father to son. And virtually all genes on the single X-chromosome in men, which can come only from their mother, are expressed. This is why such things as baldness in men come through the mother’s side. Scientists have worked out the sequence of nucleotides in sections of what is called the non-recombining portion of the Y-chromosome (NRY). The differences reveal how closely related male members of different populations are. Scientists have constructed a family tree for the human Y-chromosome (“MtEve” [The Trees]). Large sections of it came from such witnesses for the defence as Hammer and Horai (1995), Karafet et al (1999), Underhill et al (2001) and Ke et al (2001). We are getting to know a great deal about migration of at least the male half of the human population. But we cannot automatically assume these movements always indicate population migrations that included women. It is not only married men who migrate to new regions. Any man who travels a lot can spread his genes, including his Y-chromosome, quite widely. For many reasons women’s genes usually spread more slowly.

Nuclear DNA

DNA is ultimately responsible (via RNA) for making proteins. Living matter is made up largely of protein. Matt Ridley (2000) writes “almost everything in the body, from hair to hormones, is either made of proteins or made by them”. Proteins are just long chains of amino acids. Twenty amino acids are commonly found in nature. Each amino acid is, in effect, coded for by a particular sequence of three nucleotides on the DNA. The pattern of nucleotides on the DNA therefore ensures a particular protein always has the same sequence of amino acids; but any mutation in the DNA can change some aspect of the protein it is responsible for and even the creature itself. It has been shown statistically most mutations seem not to have any effect though (Lewin 1999).

Any harmful protein change would usually be eliminated during foetal development, or possibly even before conception. Mutations that provide an advantage for any individual with it are probably very few and far between. Harmless protein changes move slowly through a population, as individuals with the mutation move around and leave descendants. But particular mutations are usually concentrated in particular geographical regions. The book “History and Geography of Human Genes” by Cavalli-Sforza et al (1994) can provide many hours of contemplation. It contains about 500 maps of the distribution through the world of various genetically controlled blood proteins and enzymes. Further processing of this data by a system called “principal component analysis” has provided maps of mutations that tend to occur together in clumps. The map of the first principal component for each region shows the distribution of the greatest level of genetic variation within that region.

Because, by definition, the maps pick up only genes that display regional variation the two opposite extremes are usually each concentrated in separate regions, but they merge gradually into each other. Once the regional genetic combination that makes up the first principal component is removed the next most common one (second principal component) is revealed, often showing a completely different pattern, and so on.

Studying these maps gives us an indication of the migration of different human populations around the world and the defence will call on Cavalli-Sforza’s maps many times as evidence in favour of the defendant. Of course humans, like all species, share the vast majority of their genes with each other. That is why we all look roughly the same but this case will concentrate mainly on those genes that vary within each species and group of species.

Although DNA evidence is readily accepted in Courts of Law to establish close relationships or the identity of individuals it does seem as though many of us are unwilling to accept DNA evidence of relationships in the present case. Of course the same mutation at the same point on the DNA molecule in two different individuals at different times may lead to our misinterpretation of the evidence in some cases.

So at conception you received genes from each parent in the ratio of 50:50. Some research suggests that the egg is able to select the best sperm, but the selection of genes from each parent is basically random. So when you were conceived you took half your genes from your father and half from your mother which, mixed together, make up your characteristics.

Dominant and Recessive Genes

Each of your genes provides two possibilities, one from your mother and one from your father. Any gene always expressed as a characteristic is called the dominant gene. By convention the dominant gene is written with a capital letter, e.g. “B”. The lower case letter, “b”, is used for the recessive (the one that usually doesn’t show). Because each individual has two genes for each characteristic the only possible combinations are “BB”, “Bb”, “bB” and “bb”. You can put the gene from your mother or your father first but be consistent. It sometimes makes a difference whether the gene comes from the mother or the father (Jones 2000). The reasons for this are complex and needn’t concern us. “BB” and “bb” are called “homozygous” (the same gene on each chromosome) and “Bb” and “bB” are called “heterozygous” (different gene on each chromosome).

Dominance can actually be complete or incomplete. In the case of complete dominance the first three examples above would all look the same for that characteristic. Just the one individual in four with the combination “bb” would look different. In cattle the black colour is dominant. In that case “B” could represent a dominant gene for the colour black and “b” represent a recessive gene for the colour white. The combination “bb” would be the only one that would produce a white animal. The other combinations would all be black.

A particular gene always occurs at a particular section of a chromosome. In each individual only two options are available because they have pairs of chromosomes, one of each pair from each parent. But in the population as a whole there may be many different genes available for that place. Human blood groups, for example, have three options on the chromosome: A, B and O.

Four blood groups exist: O, A, B or AB. O is recessive and so always homozygous (oo) but A and B can be homozygous (AA and BB) or heterozygous with O (Ao and Bo). AB is an example of incomplete dominance. This is what makes us all so different. And in the case of the B and b example a gene for a reddish-brown colour could be available as well as genes for black or white. This complicates things but dominance may still be complete. Black may be dominant over both red and white, and red dominant over white for example.

Some genes are co-dominant or cumulative: the heterozygous “Bb” or “bB” can be sort of halfway between the homozygous “BB” and “bb”. For the example of black and white given above the heterozygous individuals would be some shade of grey. With the addition of the red gene a combination of red and black could give a dark brown or bay colour, and red and white a fawn or dun colour. In some cases heterozygous individuals (“Bb” or “bB”) are actually at an advantage over either homozygous extreme. This is one of the things that ensure “hybrid vigour” or “heterosis”. In practice, though, characteristics that vary along a continuum between two extremes are usually the product of several different pairs of genes at different places even on different chromosomes, which individually demonstrate complete dominance.

In actual fact black is not the dominant colour in all animals. For example white is dominant in cats. In this particular case the gene that gives rise to the white also leads to deafness and white cats, especially males, are usually deaf (Jones 2000). This means there has been what is called “selection” against white cats, otherwise all cats would be white (I would bet there has also been selection against white cats for other reasons as well. Except in snow a white cat is easier to see when it is hunting or being hunted for instance).

The concept of selection has been borrowed from farming. Farmers control which individuals in their dairy herd, for example, will be able to leave more genes in the form of descendants. They do this by “selecting” which animals to either breed from or get rid of. In effect nature does much the same thing with animals and plants. If individuals with a particular characteristic are less successful at breeding those without the characteristic will make up the population numbers. This is called natural selection.

Selection keeps disadvantageous mutations at a low level. But if a dominant gene appears in a population it obviously spreads very rapidly through the generations if individuals with it leave more offspring that in turn leave more offspring etc. A recessive gene spreads more slowly because selection can operate only on individuals where the gene is expressed, i.e. those born with a double recessive. If individuals with a double recessive leave more offspring after many generations the whole population will have become double recessive. The dominant gene will then be extinct. By that time another advantageous recessive may have arisen in the population at the same point on the chromosome. In this way a recessive gene can become dominant but not, of course, over any gene it had previously been recessive to. The defence will expand on this in “Hybrid vigour and Inbreeding” [Wave Theory of Evolution].

And I’m afraid it is not really even that simple. Many animals have genes that make the two colours paler, appear in patches, stripes or spots on their bodies, and some even have three colours. Calico, or tortoiseshell, cats for example can have three colours. Most genes for colour in cats happen to be carried on the X-chromosome. To get a tortoiseshell and white cat there has to be a red gene on one X-chromosome and a black gene on the other X-chromosome as well as other genes that promote patching with white. Because males have only one X-chromosome tortoiseshell cats are usually female. Any males that are tortoiseshell-coloured must have an extra X-chromosome and they are sterile.

Genetic information therefore is carried in a way that allows an almost infinite variety of possibilities. A number of genes are available for each point on the chromosome and a number of points on the chromosome can carry similar genes. There are also genes responsible for switching on or off other genes. In fact most characteristics are almost certainly the result of a series of such genes (Ridley 2000). For any characteristic there is a sort of hierarchy of genes. Whether a gene is dominant or incompletely dominant is probably also ultimately under genetic control.

For practical purposes we can regard populations, or whole species, as being simply collections of genes, or nuclear DNA, in various proportions. The study of this is called population genetics and the defence will use information gained from studying cattle to explain the idea many times during this case. Because a great deal of information is available for cattle they are ideal for the study of practical genetics. Not only have desirable qualities been bred for; the change each generation can actually be measured.

Meat quality, weight and growth rates for beef cattle progeny can be measured accurately. In dairy cows milk production, protein and fat percentage in the milk, overall size, temperament, teat placement and udder shape are all to some extent genetically controlled and can be measured, or at least subjectively judged. All these individual traits have what is called a bell curve distribution. As you move away from the most common type in any direction numbers fall off in the shape of a bell. The further from the majority you get the fewer individuals there are. The jury will eventually understand how we can see that in effect each individual gene travels through a population on its own independent wave.

My grandfather milked Shorthorn and Red Devon cattle breeds. By the time my uncles took over the farm Jersey cattle had become the fashion. But they didn’t need to buy a whole new herd. They just formed a sequence of hybrids with Jersey bulls. After three cow generations the herd was ⅞ Jersey (“Pedigrees” [Ancestry]). They looked like Jerseys but when I was a child some cattle in the herd still had pink noses or were brindled, a throwback to the earlier breeds. Their fathers had Shorthorn or Red Devon ancestry too.

When Friesian cattle then became popular it was again possible to gain a Friesian herd by the same method. But the mitochondrial DNA of many Friesian cows in the New Zealand dairy herd goes right back to Shorthorn or Red Devon cattle.

Mitochondrial DNA

So far we have been dealing with nuclear DNA, the DNA responsible for your genes. But there is another type of DNA in your body. It is called mitochondrial DNA (mtDNA). This DNA is not involved with the formation of genes (Jones 2001) and it occurs as a circular molecule (the ends are connected). Human mitochondria each consist of just sixteen and a half thousand pairs of the nucleotides: A, T, G and C. Each cell of the human body may have up to ten thousand molecules of mtDNA but most have far fewer. Mitochondria occur outside the nucleus and are known as the powerhouse of the cell.

They produce the proteins responsible for digestion within the cell. These proteins are involved in the production of ATP (adenosinetriphosphate) from various acids produced in the body. This process takes up oxygen and produces carbon dioxide and water. In the vast majority of individuals all the mitochondria in every cell have exactly the same DNA but mutations do occur. If the mutation happens in an egg cell it is passed on to the offspring.

The egg cell needs its mitochondria for metabolism and cell division but the sperm’s mtDNA is effectively discarded and lost at fertilization (Jobling et al 2004). Therefore the mtDNA is passed unchanged from only the mother to the child for thousands of generations. In fact the mtDNA does change over time (mutations). The rate of this change and the regularity of the change have been greatly debated by scientists; i.e. does it have a sort of half-life? How much does it change, say, in a thousand years? Is the change totally random or does selection act on these changes? It is now generally accepted that some sections of mtDNA change quite rapidly and regularly, and it has been shown that one parent-child comparison in forty has a mitochondrial mutation (Jones 2000). Because there is a great deal of mtDNA in each individual, and it is a relatively short chain, it has been the easiest DNA to extract and to study.

Like the Y-chromosome, the sequence of the nucleotides in sections of the mtDNA has been worked out for individuals of many species. The accumulation of differences in the sequences can be used to indicate the relationship of various groups of animals and humans through their mother’s ancestry. If the mtDNA is only a little different it is presumed they are closely related and of course this would be so, no matter what the rate of mutation.

Again, like the Y-chromosome, examination of the mutations in human mtDNA has been used to construct an evolutionary, or family, tree. From this it has been concluded we all descend from a single woman who lived in Africa. We will meet her again and see her family tree in “MtEve” [The Trees]. But before then the defence needs to explain a few more things.

Studies of the changes in mitochondrial DNA and the Y-chromosome have been very useful in helping us understand our origin but we need to consider other evidence before we jump to conclusions. The first thing we need to consider, and explain, is the present distribution of human genetic variations.

See next :: Human Evolution On Trial - 'The Human Star'

Witnesses Called

Cavalli-Sforza, Luigi Luca, Menozzi, Paolo and Piazzi, Alberto (1994) The History and Geography of Human Genes. Princeton University Press, New Jersey.

Cavalli-Sforza, Luigi Luca and Cavalli-Sforza, Francesco (1995) The Great Human Diasporas. Addison- Wesley

Hammer, Michael F. and Horai, Satoshi (1995) Y Chromosomal DNA Variation and the Peopling of Japan. Am. J. Hum. Genet. 56: 951-962

Jobling et al (2004) Human Evolutionary Genetics. Garland Science, New York.

Jones, Martin (2001) The Molecule Hunt. The Penguin Press, London.

Jones, Steve (2000) Almost Like a Whale. Anchor, London.

Karafet et al (1999) Ancestral Asian Source(s) of New World Y-chromosome Founder Haplotypes. Am. J. Hum. Genet. 64: 817-831.

Ke et al (2001) African Origin of Modern Humans in East Asia. Science Vol. 292 1151-1152

Lewin, Roger (1999) Patterns in Evolution. Scientific American Library, New York.

Ridley, Matt (2000) Genome. Harper Collins, New York.

Stringer, Christopher and McKie, Robin (1996) African Exodus. Random House, UK.

Underhill et al (2001) Y-Chromosome Haplotypes and Implications for Human History in the Pacific. (pdf) Human Mutation 17: 271-280.

Human Evolution on Trial - The Human Star

2009-06-20T17:40:00.000+02:00

Human Evolution on Trial - The Human Star

During the 2000 Olympics I heard a TV announcer say something to the effect “it’s amazing how Africans dominate middle distance running.” My immediate reaction was they were dominating sprint and long distance running as well. People of West African origin, especially Afro-Americans with possibly some European genes, dominated sprint. East Africans dominated long distance. Several African groups had dominated middle distance running, especially those across the north from Morocco to Northeast Africa. This indicates that Africa contains different regional genetic groups. In fact a great deal of evidence shows there is more human genetic variation in Africa than there is in the rest of the world. This fact is used as evidence in support of the idea humans originated in Africa. Human genes are not distributed evenly around the rest of the world either though. We could say there are several regional kinds of human.

Although populations from opposite extremities of Europe and Asia look different it’s possible human movement across these continents at various times has obscured many earlier regional differences. We actually know several movements from history.

The boundaries are impossible to define. But blond-haired, pale-skinned people with blue eyes and relatively prominent noses were originally concentrated in the northwest of Europe. People with flatter faces, narrow eyes, straight black hair and so-called yellow skin are found mainly in the Far East, especially the Northeast. In the extreme Southeast we find Australian Aborigine and Melanesian people. Inspection reveals that all these extremes merge gradually into Asia, a series of what are called clines. For example people with mousy coloured, red or brown hair border the blond haired population. In biology the word cline is used when there is a gradual change in the appearance of a species across its geographic range.

Geography

I became aware of just how important geography was on human movements through my interest in music, especially the blues. I noticed that, with a couple of minor exceptions, the regions of the United States of America where the early blues singers had come from were all less than 200 metres above sea level. This was obviously not because the air was too thin for blues singing above this fairly low altitude. Rather it defined the area where cotton, tobacco and other crops requiring a large amount of cheap labour were grown.

The first Africans who went to America came mainly from the Gambia and Senegal Rivers at the very western tip of Africa. The blues seems to derive most of its African musical influence from these first arrivals even though many more slaves actually came from further south, even from as far south as Angola. It appears the first arrivals dominated the developing Afro-American culture. Some words from languages of this region have even entered English.

The blues were usually sung in English in fact and so we can safely say there was a European element in it as well. And Rock ’n’ Roll is just one more time that African music has influenced the white peoples’ music in the region. In spite of division between these two groups the people and cultures have mixed. There has even been quite a bit of gene flow between the races. African Americans for example usually have between one twenty-fifth to one third European ancestry (Olson 2002 and Jobling et al 2004).

This sort of population movement and mixing has happened almost continuously. In fact we can trace the pattern right back to, and even beyond, the origin of our species. But first we need to realise that the various technological, cultural and genetic expansions of humans around the world have been like ripples or waves in a funny shaped pond. Barriers to the expansions such as seas, deserts, tropical rain forest and mountains have continually deflected the ripples or even altered them and sent them back.

Africa, for example, is almost entirely surrounded by sea. Many ripples have been confined to Africa. Except for during some ice ages and more recently with the development of boats (and more recently still aircraft) the exit and entrance has been confined to the Sinai area for virtually all our history, our evolution.

Deserts and forests expand and contract with changing climate. They too have often influenced human ability to move freely around the world. For example within Africa the Sahara Desert has periodically been a barrier. Evidence shows it has been much moister at various times though. In fact it was “semi-arid grassland” again until 5500 years ago (Jobling et al 2004).

The banks of the Nile have also occasionally provided a route north through the region. Deserts have also formed at times in Arabia, India and Central Asia (not to mention Australia and the Americas). The tropical rainforest and swamp of the combined Ganges and Brahmaputra River deltas seems to have kept Southeast Asian and Indian populations fairly separate in the past, at least until boats were invented, although it is today one of the most densely populated regions on earth.

The development of glaciers during cold periods makes mountains even more effective barriers but they have always been there during human expansion. Outside Africa the Taurus Mountains of Turkey and the Zagros Mountains of Iran form the first mountain barrier to human expansion. Beyond them the Himalayas, Pamirs and Hindu Kush mountain ranges of Central Asia have always interrupted human movements. In fact the presumably ancient remnant language Burushaski survives in an isolated valley in this mountain complex.

Although the Black and Caspian Seas have periodically been joined to each other north of the Caucasus Mountains the mountains themselves seem to have been virtually impassable throughout human history. In Europe the Carpathian Mountains seem always to have been a barrier to free movement and the Ural Mountains and the swamps to their east became significant towards the end of the last ice age (Clark 1969), as did the mountains of Northeast Siberia and Alaska. The Chin Ling Mountains served for a long time to separate the people of North China from the Hoabinhian people of South China (Bellwood 1978).

A Map

I will now present a map of the world showing these tropical rainforest, desert and mountain barriers. But seeing I’m from New Zealand I’ll put New Zealand at the top left so we can examine the rest of the world more easily. This also puts at the top the part of Africa where humans seem to have first developed. Human movement into the Americas is comparatively recent and so I’ll hide most of that double continent. I have drawn ovals around each region where the human populations are most different. The horizontal lines represent degrees in latitude from the equator. The dotted lines show shorelines at times of low sea level.

If you look at the map you will see the distribution of humans round the earth can be represented diagrammatically by a five-pointed star. The extremes of human appearance are found at the points, with the rest of the population grading from the middle and from neighbouring points on the star. I’ll call the five points “East Asia”, pre-European “Australia”, “South and East Africa”, “West Africa” and “Northwest Europe”. The gap between Southeast Asia and Australia is called Wallace’s Line.

Although I have used Australia to demonstrate the type found at one point historically humans didn’t begin to move into Australia until about 50,000 years ago. But people of a similar physical type must have been present in mainland Southeast Asia from at least that long ago. A migration of people south from the East Asian point, perhaps as recently as six thousand years ago, has gradually diluted earlier human genes in that region from.

Here is the diagram of the human star

There are also little sub-points between the main points of the human star. They represent populations that are a combination of people from the middle of the star and the points on either side of them. Apart from the Indian subcontinent most have been occupied only since the end of the most recent ice age, about 10,000 to 12,000 years ago.

For any species the individuals at the geographical extremities of its distribution will be the most different. This has been recognised for a long time (Mayr and Diamond 2001). From the middle genes or ripples can flow in many directions but at the points gene flow reaches a dead end (if it reaches the point at all). On the other hand while ripples can flow from a point into the middle of the star or to a neighbouring point they are less likely to reach a more distant point.

I have divided Africa into two main points because most scientists would agree that, until relatively recently, the population of the two regions was quite different. The many African languages from the two points have actually been grouped into just four families. Within the point I have called South and East Africa the Khoisan language family (from the south) and Nilo-Saharan (from the northeast) may be distantly related to each other. There is evidence an expansion of Nilo-Saharan languages south at some time has isolated some northern Khoisan languages though.

The word Khoisan is commonly used to combine two Southern African groups: Hottentots (Khoi) and Bushmen (San). Anyway Khoisans and some Ethiopians are genetically closer to each other than they are to West Africans (Cavalli-Sforza et al 1994). In the last few thousand years people speaking Bantu, from the third African language family (Niger-Kordofanian), have migrated from the West African point through the middle of the South and East African point.

They have interbred with, or replaced the original Khoisan people (Jobling et al 2004). This has interrupted what had probably earlier been a cline from Ethiopians to Khoisans. Many tribes in the region show by their appearance, though, they are a genetic mix of types from the two neighbouring points of the star, West Africa and South and East Africa, and elements of the Khoisan languages survive in some Bantu languages, for example “clicks”. The Bantu people proper have arrived in the southeastern tip of Africa only in the last three to five hundred years. The fourth African language family, Hamitic, is spread across North Africa and into Ethiopia.

Before we leave Africa and look in turn at the two bottom, or northern, points of the star we’ll look briefly at the little subpoints.

The Pygmies were probably the first people into the rainforest of the Central West African sub-point and they probably evolved in it. Cavalli-Sforza (1995) starts his book “The Great Human Diasporas” with an account of the Pygmy people. He states the Pygmy populations do not share a common language. Their languages have been adopted from other people they have come in contact with. The sub-point has more recently been slowly colonised by people from the neighbouring points of the star, especially by West Africans.

I have made India a sub-point, mainly to give myself five points on the star but in fact it does show characteristics of a sub-point. Entrance and exit seem to have been difficult and a volcanic eruption in Indonesia around 70,000 years ago may have emptied it. People there have probably resembled a mix of East African and Australian Aborigine types for much of human history but very few early human remains have been found. The modern people of India are the result of mixing of any original population with more recent movements, from both the west and the east, of Dravidian-speaking people and East Asians. The expansion of Indo-European people, originally from the middle of the star, has even more recently had a huge influence on Northern India (Mallory 1989).

The people in the sub-point of Island Southeast Asia and the Pacific are a sort of hybrid between the Australian Aborigines and the East Asians. I’ll have to leave the American and Mediterranean Islands sub-points for another day.

The White Man

Now for the remaining two points on the star, Northwest Europe and East Asia.

One of the things that encouraged me to take on this project was that during a discussion on environmental effects on human populations one of my brothers wondered where white skin and blue eyes came from.

This brings us to the question of “race.” It is interesting that any study that ranks human races along a scale of superiority or advancement always surprisingly finds the race of the person making the study is the most superior or advanced. Throughout history most of us have probably believed our own tribe, culture and mythconceptions are superior to others. They are the ones we know best.

More than 2300 years ago Aristotle claimed that some people were naturally inferior and should be ruled by superiors but the idea whole races can be inferior may be a fairly recent development. In fact it has been suggested the idea evolved in order to justify the use of slavery in the intensive farming systems developed in the Americas in the last 400 years (Davidson 1974). The idea of white supremacy was further refined, especially from the 1880s to 1920s, to justify European imperialism.

History shows we humans are capable of justifying anything if we use a little creative thinking. There is certainly no doubt the slave trade disrupted sub-Saharan Africa to an incredible extent. Any excuse that slavery was long established in that continent is irrelevant. Slavery and the use of convict labour had been common everywhere, but huge numbers (perhaps more than ten million, a large proportion of the population) were taken from Africa. Many more than that number were killed during the required raids. The continent has still not recovered from the disruption caused by this economic exploitation.

Humans in different regions have certainly had different selection pressures applied to them by the environment. People who have lived for many generations under tropical sun have developed very dark skin probably as protection from the sun’s ultra-violet radiation (see for example Stringer and McKie 1996) but paler skinned people have survived well enough away from the tropics.

Some scientists suggest the different regional human varieties or races could have developed as a result of “sexual selection”. But it is difficult to believe ancient humans behaved any differently to the way many sexually active humans behave these days. Any preference individual humans may have to mate with blond people for example is unlikely to be instinctive. It is much more likely to be due to cultural factors. I suggest sexual selection is unlikely to be the cause of human variation.

The white colour in humans is often said to have developed in order for the human body to make vitamin D under conditions of short daylight hours (again see for example Stringer and McKie 1996). It is possible to get enough vitamin D from our diet though (Jobling et al 2004). Besides, humans didn’t get anywhere near the Arctic Circle (66° north), where vitamin D production would be a problem, until more recently than 30,000 years ago. By then they were fully clothed. Even some supporters of Intelligent Design would probably accept that the development of white skin probably happened before clothes were invented.

It is likely that in prehistoric times humans were able to reach at least latitude 50° north during periods of warmer climate. For example in Europe even Neanderthals were able to exist to about latitude 50° north for much of their existence. This was both by genetic adaptation to the cold and because ocean currents have usually warmed Western Europe a little compared to continental areas further east. But it is also almost certain that during colder periods Central Asian populations especially have been pushed south beyond 40° north. This has separated the Northwest European and East Asian populations at times. It is my bet natural selection in each region led to two different adaptations to an environment with winter snow.

It might be significant that until recently so-called white people were confined to the area where the natural cover is northern deciduous forest. White people actually become brown in summer through the process of tanning. This colour change is reasonably common in many creatures that live in regions of winter snow. Ermine, arctic foxes, varying hares and two or three species of grouse, or ptarmigan, are animals I immediately think of. For any other creature that had white hair, blue eyes and changed from white to brown with the seasons we would have no hesitation in pronouncing it was an adaptation to winter snow. Do we see here the assumption humans somehow obey a different set of biological rules? Of course in other animals the colour change involves a change of hair, fur or feathers but we know nature is remarkably clever at achieving the same result by different methods.

A Cline

Luigi Luca Cavalli-Sforza (1994 and 1995) has done a huge amount of work mapping the frequency of various human blood protein markers and enzymes. His map of the most important genetic landscape of Europe, the first principal component, accounts for nearly 30% of the genetic variation in that point of the human star (map 2).

We could say the map is a bit like a weather map. The darkest shading of the opposite types of cross-hatching are the equivalent of pressure systems. They show the greatest concentrations of two different and opposite genetic combinations within the European population. The bold dashed line can be thought of as being a sort of boundary between the two genetic extremes although in fact they merge gradually. People at the opposite ends of this European cline tend to have different skin and hair colouring but the map is actually based on difference in blood proteins and enzymes not skin colour.

Cavalli-Sforza interprets this map as reflecting the spread of farming into Europe from the Middle East. Some people feel it also reflects the expansion of genes from Northwest Europe (Jones 2001). This has happened with Vikings, Germans and Celts within historic times and there were almost certainly prehistoric movements. In any case the map demonstrates the Northwest European point is genetically different from the middle of the star and there is a gradual merging of the genes, or a cline, across Europe.

Maps of other parts of the world given in “The History and Geography of Human Genes” (Cavalli-Sforza et al 1994) show similar genetic gradients or clines in other points of the star. In fact the phenomenon is found throughout nature. But of course different species may each have a star of different size and shape, especially a different number of points. This will depend on their individual geographic distributions.

Many genetic ripples have left their mark around the earth and can be traced. For humans we can also trace technological and cultural ripples. We can use all this to explain the origin and evolution of our species. In fact all species.

Altitude

But we’ll return to our human star. The people of East Asia developed a different response to a cold environment. They have very little facial hair compared to other human populations. This could be an adaptation to a very cold environment. If you have seen photographs of polar explorers or mountaineers you will have seen the buildup of ice in their beards from their breath. It would not have been an advantage to have a permanent ice-block around your face all winter. East Asians show several adaptations to a high light intensity environment and so it seems fairly likely that they originally developed in a reasonably treeless region at a fairly high altitude.

For example their yellowish skin contains only a small amount of melanin (the stuff that makes skin black or brown) but the outer layer of their skin is packed with keratin (Bellwood 1978). This reflects sunlight very efficiently and resists the penetration of ultraviolet light. But East Asians’ most obvious feature is what is called the Mongolian eye-fold. Anyone who has been on open snow in full sunlight without sunglasses will know what a great advantage this development would have been. Glare is also a problem in desert. The Khoisan of the Kalahari Desert for example also have narrow eyes, but no eye-fold. Cavalli-Sforza (1995) describes them as having “almost Oriental features”. East Central Asia is fairly dry and summer desert conditions may have reinforced this characteristic in East Asians.

So how long ago did these sorts of differences in human populations develop?

The breeding of domestic animals shows selection by humans can change such things as colour, shape and size quite quickly. Change can also be rapid in nature. Some bird species that can have been isolated on Long Island in Northern Melanesia for only 400 years have already started to look noticeably different to the populations that are presumably their ancestors (Mayr and Diamond 2001). Perhaps the changes in the human species (in zoological terms Homo sapiens, “man the wise”) have all happened quite recently.

In fact some people claim that all this change in human populations has happened only in the last six to ten thousand years. Even that the different kinds of human descend from just three or four pairs of human survivors on an ark from some indeterminate time in the past. Perhaps the much longer time since modern humans are believed to have come out of Africa is sufficient. I suggest that population movement has been too rapid for that sort of change to have developed even in that time.

The evidence indicates the Tasmanian Aborigines were as dark as (and possibly darker than) mainland Australians though they existed for a very long time in regions of winter snow beyond latitude 40° south. It was obviously not long enough or perhaps far enough south to develop whiteness. On the other hand natives of the Andes are exposed to some of the highest ultraviolet radiation in the world but haven’t been exposed to it long enough to develop black skin (Stringer and McKie 1996).

Is it possible the development of a white skin or an eye-fold extends as far back as 200,000 years ago, the time of Neanderthal / Archaic Homo sapiens? Or even further back to the days of Homo erectus? Of course many people believe the evidence shows these species have made no contribution to modern human genes. However the wave theory of genetic, cultural and technological evolution allows us to see how they may have.

See next :: Human Evolution On Trial - 'Pedigrees'

Witnesses Called

Bellwood, Peter (1978) Man’s Conquest of the Pacific. Collins, Auckland.

Cavalli-Sforza, Luigi Luca, Menozzi, Paolo and Piazzi, Alberto (1994) The History and Geography of Human Genes. Princeton University Press, New Jersey.

Cavalli-Sforza, Luigi Luca and Cavalli-Sforza, Francesco (1995) The Great Human Diasporas. Addison- Wesley

Clark, Grahame (1969) World Prehistory. Cambridge University Press, UK.

Davidson, Basil (1974) Africa in History. Paladin, UK.

Jobling et al (2004) Human Evolutionary Genetics. Garland Science, New York.

Jones, Martin (2001) The Molecule Hunt. The Penguin Press, London.

Mallory, J. P. (1989) In Search of the Indo-Europeans. Thames and Hudson, New York.

Mayr, Ernst and Diamond, Jared (2001) The Birds of Northern Melanesia. Oxford University Press, New York.

Olson, Steve (2002) Mapping Human History. Houghton Mifflin Company, New York.

Stringer, Christopher and McKie, Robin (1996) African Exodus. Random House, UK.

Human Evolution on Trial - Pedigrees

2009-06-20T17:35:00.000+02:00

Human Evolution on Trial - Pedigrees

Comparing the breeding of domestic animals to evolution has been criticized since Darwin’s time but sanity tells us there must be similarities. In fact Steve Jones (2000) says “the best place to see evolution is on the farm”. The characteristics selected for may be different but the resulting drift in population genetics and reduction of mitochondrial DNA and Y-chromosome lines are very much the same. Both processes rely on “selection”, that is the culling or extinction of individuals in a population.

Individuals of a species vary. Animal breeders select the individuals they wish to breed from: the ones that exhibit the characteristics they would like to have in their herd for example. In evolution the same process is sometimes called “survival of the fittest” although this expression seems to have been first used to justify a particular economic theory.

In both evolution and breeding the most important process is in fact culling, the elimination of unwanted individuals. The antelope that fails to get away from the lion is more important for evolution than the many that manage to escape. Selection has to work on a population as a whole. The defence will show in “Hybrid Vigour and Inbreeding” [Inbreeding] that, apart from cloning, it is useless to simply breed from the best individuals.

Ancestry

As part of their breeding program farmers usually keep a record of each animal’s ancestry, its pedigree. I now present a very important illustration of nuclear and mitochondrial DNA and the Y-chromosome. This is an important illustration because it starts with my pedigree. We’ll look at yours next. Here is my “whakapapa” or ancestry, as it would be set out in a studbook: - By convention the male from each pair is written on top.

Of course my pedigree doesn’t just stop here but I don’t know all sixteen names of my great great-grandparents even in just the next column. I have one great-grandfather’s surname and his NRY or non-recombining portion of the Y-chromosome (remember the Y-chromosome passes from father to son). But all eight ancestors in the right-hand column provide my genetic or nuclear DNA. Probably roughly in equal portions but I happen to look superficially most like John Putt.

My mitochondrial DNA comes totally from Jeanie Wright who got it from her mother etc. Of course my brothers and sister all have exactly the same pedigree but their name replaces mine. The selection of genes is still 50% from each of our parents even though it is a different assortment of 50% for each of us. We all have the same mtDNA though and my brothers have the same NRY.

You can now construct as much of your own pedigree as you are able to. Remember to put the male of each pair on top: -

You have two parents, four grandparents, eight great grandparents, sixteen great great-grandparents, etc. The number of ancestors doubles each generation. By ten generations there are over a thousand places for names in the right hand column of your pedigree. Therefore if we assume one generation is 25 years your genetic makeup is the product of the contribution of one thousand people living about 250 years ago. Expanding it back only 500 years, or 20 generations, would give a huge list of over a million names in the column at the right; this at a time when the total population of England, for example, was only about three million. Expanding it back 5000 or 50,000 years gives an unimaginably large number of ancestors but we’ll confine it to a more manageable 500 years for now.

In this column of over a million ancestors from 500 years ago your mtDNA comes only from the individual at the bottom of the right hand column. Remember that, although the mitochondrial DNA is passed to all of a particular woman’s children, it is only her daughters who will pass it on to the next generation. If you are a male the main branch of your Y-chromosome will come only from the individual at the top of the column. If your surname goes back that far, and nothing has interrupted the sequence, your surname may also go back to this individual but that is a big ask. Any children you may have will automatically have the million ancestors in your partner’s pedigree added in. Your sons will all have their father’s Y-chromosome but all your children will have their mother’s mtDNA.

The jury can see that genealogies that concentrate only on one line grossly distort reality. I suppose it is theoretically possible half your genes could come from just a single one of these million ancestors and the other half from another one but this is very unlikely. Anyway even if you have as many as 100,000 genes more than 90% of these ancestors from just 500 years ago have no genes surviving in you. Many of those genes could come to you from other ancestors who shared those genes though. Some of those genes lost in your pedigree may survive in other people alive today. Other genes may be extinct.

If you could actually list the million names in your pedigree from five hundred years ago the same pattern of names would appear more than once in that column. Any repeated names on the list represent the level of inbreeding. In fact to guard against inbreeding animal breeders look for common ancestors only four or five generations back in a pedigree, but any population not infinitely large will have some level of inbreeding, i.e. all populations of all species (Falconer 1964). That’s why their members look similar to each other.

If you have been observant you may have noticed the surname Wright appears twice in one column of my pedigree. I actually have no idea how closely related Elizabeth and Jeanie were but let’s say they were sisters. This would mean they had the same mother and father. These two names would therefore appear twice in the next column to the right. Numbers 11 and 15 and numbers 12 and 16 would each be the same name. Of the thirty-two names that would be in my pedigree the next column back, the list from 21 to 24 is repeated as numbers 29 to 32. And so on. So in the column of 1,048,576 names from 500 years ago numbers 655,360 to 720,896 are exactly the same as numbers 917,504 to 983,040. Got that? In the column of over a million names in my pedigree there would be a repeated section of over sixty-five thousand names. Even within these 65,000 names there will be repeated sections and there would be other repeated sections elsewhere in the column. We will return to “Hybrid Vigour and Inbreeding” and how the wave theory of evolution works in Part II.

Populations

So far we have been considering pedigrees only from the perspective of the individual on the left, you or me. If we move one step to the right, to your parents, we realise you may not be their only child and they may not be single children. You could now attempt to do a family tree of one pair of your grandparents. They probably had several children and these will be your aunts and uncles. They will share many of their genes with one of your parents and fewer with you. Your aunts and uncles would have married people with completely different pedigrees to yours and their children will be your cousins. They will share even fewer genes with you. In other words if you combine your pedigree with the family trees of each of your million ancestors you can see the population becomes a huge network of genes. If you have ever been to a family reunion you may be able to imagine just how complex that network can be.

This brings us back to the subject of population genetics. Knowledge of what can cause reduction in Y-chromosome and mitochondrial and nuclear DNA lines in a population will be able to help us interpret the evidence for the evolution and distribution of our species.

As an illustration the defence will use the list of your one million different ancestors from 500 years ago and assume population numbers have stayed the same over the generations since that time. This is probably what happens on average for most species although in practice the numbers fluctuate, sometimes wildly, between the generations. For example Steve Jones (2000) gives a brief account of the complex interactions and fluctuations in numbers of snow grouse, lynx, snowshoe hares, willow and birch trees, and squirrels, coyotes and ravens within a small region. The so-called balance of nature is very complex and constantly changing. The more recent steady population explosion in humans has not been our normal state. It is impossible to decide from the evidence exactly how many humans there have been at various times during our history though. The total human population may have been as low as ten million (the size of London today) or even lower (Jones 2000) for much of our past. Anyway we can be sure numbers have fluctuated wildly.

To maintain population numbers of a species each couple, on average, must produce two offspring that survive to breed, that in turn produce two offspring, etc. Let us assume the average number of offspring per pair is four. This is not a large number, even for a human, as many families contain more than this number of children. Four offspring allows a selection rate of 50% but first let’s look at the male / female ratio. Each birth has a 50:50 chance of being a male (or female if you prefer), and so we get the following possibilities:

Just sixteen combinations are possible and Couple No. 1 leaves no female offspring and Couple No.16 leaves no male offspring. Therefore on average one female in sixteen would leave no mtDNA in the next generation and one male in sixteen would leave no Y-chromosome. Of course any close relatives would have the same mtDNA or Y-chromosome in practice but we’ll assume for this illustration that all the couples are unrelated.

At a 50% selection rate the diagram looks the same but what the letters stand for changes to “M” for mate and produce the next generation of offspring and “F” for fail for some reason or other to produce offspring that survive and breed. Once again one in sixteen couples fail to leave any mtDNA or Y-chromosome but this time through lack of any descendants. The combined loss of mtDNA lines (for example) is not simply two out of sixteen each generation. One occasion in sixteen multiplied by sixteen will be the elimination of an all-male family. In the next generation there will also be some families that already have several lines. Because they are less likely to be eliminated the rate of elimination slows. I have read that in a population of a fixed size mtDNA lines will reduce by one each generation (Lewin 1999). But I haven’t seen the maths and probably wouldn’t understand it if I had. If we accept it to be correct in sixteen generations, or four hundred years, the thirty-two survivors from the above small example would all have mtDNA from just one of the original females. And all the males would probably have just one of the original Y-chromosome lines.

Jobling et al (2004) mention that the first studies of the mtDNA of the American Indians showed they basically trace back to only four lines (“MtEve” [Interpretation]). Further studies have shown there are actually a few others although they are rare. But examination of ancient human remains in America show these rare ones were much more common originally (Martin Jones 2001). There has in fact been a reduction in mtDNA lines.

Selection

Starting with a closed population any woman who doesn’t produce a female child who survives to reproduce represents the loss of a line of mtDNA. Similarly, any male who doesn’t produce a male child represents the loss of a line of Y-chromosome. It is extremely unlikely all your 500,000 female ancestors from 500 years ago still have mtDNA lines today. Likewise for the 500,000 male ancestors and their Y-chromosomes. In theory, as it is twenty generations ago, twenty lines of each will have been lost. But I would be very surprised if any one of us actually know how many repeated names there are on our list of ancestors from twenty generations ago. Our individual pedigrees would each have far fewer than a million different names from that time.

It is quite easy to see that in time any population of limited size could be reduced to just one line of mtDNA but this may not necessarily descend from a female who had any genetic advantage at the time. Survival could be the result of almost random events. Genes from other members of the original population would still survive and so mitochondrial DNA lines don’t necessarily give a sure indication of nuclear DNA.

Many dairy farmers, for their breeding program, keep track of cow families, usually from the cows in the herd when they take over it or cows they have brought in more recently. They have to have a defined beginning or point of origin. Over time the number of their cow families reduces as they keep more offspring from the better cows, some cows die or are culled, or some cows have mostly bull calves, or dead ones. This leads to extinction of mitochondrial DNA lines in the herd. The way to maintain the line of a good cow in the herd who has had mostly bull calves is to actually keep bulls from that cow. Thus the mtDNA line may be lost but the nuclear DNA is maintained and even usually spread very widely.

Daniel Bradley and his colleagues (Bradley et. al. 1996) have researched mtDNA of Indian, African and European cattle breeds with interesting results. The mtDNA lines readily cluster into the three regions but African cattle have traditionally been divided into two types: humped and humpless breeds. Although it is known the humped, or zebu, cattle were introduced from India centuries ago Bradley’s DNA research indicates mtDNA lines cannot distinguish the humped and humpless breeds in Africa. Their conclusion was that the humped cattle are descended from local humpless cows crossed with humped bull imports. More recent studies of the Y-chromosome have shown this original view to be correct (Martin Jones 2001). The nuclear DNA of these humped breeds is now mostly from humped cattle although the mitochondrial DNA comes from humpless cattle. The defence will present other interesting examples of the independence of mitochondrial and nuclear DNA in “Species”.

Now, if we go back to these hypothetical million people from 500 years ago and imagine their one million hypothetical descendants today it is easy to see that the various genes present in the original population will not be present in the modern population in the same proportions. There will be more of some; less of others, some will have been totally eliminated and new mutations may have appeared. This is called “genetic drift”. For example blood groups other than O are rare in American Indians but A, B and AB were more common in prehistoric America. The ratios have changed, presumably by the elimination of blood groups other than O (Cavalli-Sforza 1995). Genetic drift would happen even if survival was totally random but, of course, genes are usually selected for or against. The greatest selection is usually against undesirable genes but selection doesn’t operate on the genes themselves. Selection can operate only on the individuals that express the genes.

Before we begin to follow this idea back through our collective family history though we should first examine our present ideas about that history.

See next :: Human Evolution on Trial - 'Mythconceptions'

Witnesses Called

Bradley et al (1996) Mitochondrial Diversity and the Origins of African and European Cattle. Proc. Natl. Acad. Sci. Vol. 93 pp. 5131-5135.

Cavalli-Sforza, Luigi Luca and Cavalli-Sforza, Francesco (1995) The Great Human Diasporas. Addison- Wesley

Falconer, D. S. (1964) Quantitative Genetics. Oliver and Boyd Ltd., Great Britain.

Jobling et al (2004) Human Evolutionary Genetics. Garland Science, New York.

Jones, Martin (2001) The Molecule Hunt. The Penguin Press, London.

Jones, Steve (2000) Almost Like a Whale. Anchor, London.

Lewin, Roger (1999) Patterns in Evolution. Scientific American Library, New York.

Human Evolution On Trial - 'Mythconceptions'

2009-06-20T17:30:00.000+02:00

Human Evolution On Trial - Mythconceptions

Human groups have probably sought to understand how and why they have come to be where they are since they first developed language capable of arguing over such things. This brings us to the problem of how we come to know what we think we know about history. Although history, by definition, is written we need to go further back.

Oral History

Our parents and grandparents can tell us their version of relatively recent events. We run into problems when we want to know details of events that happened before anyone now living was born. But not even two written eyewitness accounts of any event are likely to be the same. We don’t have identical perspectives or make identical interpretations. Therefore there is an immediate bias at the origin of any version of history. Before we even begin to consider the influence of any propaganda element along with all the personal (or collective) assumptions, prejudices and preconceptions.

You can understand that although written sources provide us with information for much of the world from the period since writing developed, these sources too are open to interpretation and can be unreliable. Before writing was invented, history was transmitted by stories passed from generation to generation. These stories may be as reliable as written records for relatively recent events although again we must always be aware of the point of view of the person telling the story (Sturgis 2001).

Stories about ancient events passed by word of mouth within groups of people evolve into what are called “myths”. Myths are stories that attempt to make sense of the complexity of existence. They usually include at least some speculation about the origin of the group, humans as a whole and even the universe itself. They define a beginning and are part of any group’s culture. They are often also used to justify a particular group’s claim ahead of some other group or groups. Marc Swartz and David Jordan (1980) write,

“A myth is a story which embodies the values that are important to a culture and which has an aura of sanctity about it”. In other words myths are a view of history that provide a model for behaviour. Shared stories and beliefs help unite groups or tribes. In fact writing has actually preserved many different myths from throughout the world. Studying them gives us interesting insights into the collective mentality of any culture to which they belong.

But each myth must be considered from our present perspective. Many people seem to believe oral tradition or myth is able to maintain the absolute and unaltered truth through many generations. Unfortunately of course myths and legends themselves evolve and are just as self-serving as any written source. Stories diversify fastest as different versions are retold during the first few generations.

Many completely different versions of a story circulate from soon after the events that give rise to it. The stories then mix, and they form hybrids. They undergo selection and survival of the fittest. Eventually it becomes politically desirable to have just one easily remembered hybrid version of the story. By then, many different stories will have gathered around the hero and several different heroes will have accumulated the same story. In spite of these problems even many people skeptical of written sources show a surprising willingness to accept oral tradition as truth.

Myths contain easily as much propaganda as do any government press release. Traditional stories may well be transmitted in “schools of ancient oral learning”, and punishments may well be used to make sure the stories and genealogies are remembered accurately, but the stories are still likely to be conveniently adjusted as they pass from generation to generation.

Science

On the other hand I would suggest we could regard everything we believe about our origin as serving the function of myth as defined above by Swartz and Jordan (see also Tudge 1996). Origin beliefs influence our ideas and so our behaviour. Although most of us would differentiate between myth and history in reality they are often quite difficult to separate. Most versions of history involve at least some elements of speculation and even today our myths affect our interpretations of the evidence.

But as a working definition I suggest we could say a myth is a history that appears to have originally been transmitted orally. And further, the people who believe the history can’t actually prove it by any evidence available. In many cases the myth may well be true but in others it can actually be proved incorrect by evidence now available. I will present some examples from New Zealand soon. And of course there are other ones from other parts of the world.

To find the truth about ancient events we can use science. The scientific method involves the process of examining the available evidence, speculating on a reason for it and then setting up a theory. This theory is next examined through any experiments and observations capable of either proving or disproving it. If the theory seems to account for the evidence it is presented to the wider world and eventually (often many years later) either accepted or finally rejected.

But any myth would almost certainly have originally developed in much the same way although in most cases it is not capable of proof by experiment. We can safely assume the people who developed myths were not stupid although they often had to resort to the supernatural to explain things they couldn’t understand. Contrasting beliefs are set against each other and the facts examined in both cases. Surely any belief has to fit the facts as understood at the time.

All knowledge accumulates by the interaction of ideas. In fact in some ways the creation and spread of knowledge, myths and ideas demonstrate the wave theory of evolution (“Hybrid Vigour and Inbreeding”). In other words they evolve. Ideas bounce around the world, join up, expand then rebound like ripples in the human star. Inadequate theories or wrong ideas eventually become extinct unless they provide an advantage for powerful elements in society. In that case they can last for centuries.

The scientific method as we now understand it developed in Europe as a product of the Renaissance (roughly between 1450 and 1650 AD) and many great thinkers contributed to it. The Renaissance itself had evolved gradually with the infusion of knowledge into Christian Europe from the Muslim world.

The Muslim world was far ahead of Europe in knowledge of the natural world at the time. The expansion of Islam had brought together Arabs, Mesopotamians, Egyptians, Persians, Indians, Chinese, Zoroastrians, Mithraists, Buddhists, Jews, Christians and Pagans and the community was able to combine and analyse all this knowledge. Muslims had also “made original contributions to alchemy, astronomy, mathematics, optics, surgery and medicine” (Fyrth and Goldsmith 1965).

Many ancient Greek writers, whom many people accept as being the great thinkers of the ancient world, had also been translated into Arabic. Although the Greeks made a huge contribution to mathematics (school children still hear the name Pythagoras) they valued logic and deduction more than experiment. This is not surprising. They were hampered in their science by their lack of knowledge. Advances in technology have increased our knowledge considerably since their time.

Ancient Myths

As the Renaissance flowered powerful people began to oppose the scientific method as the results began to conflict with the prevailing mythological conception of the universe. The Inquisition condemned several early scientists to be burned at the stake. Things seem to have become a little more liberal since 1619 when the Inquisition had Lucilio Vanini burned for suggesting that humans might have evolved from apes (Corfield 2001). Even as soon after as 1632 Galileo was merely placed under house arrest for the rest of his life for suggesting the earth went around the sun.

In fact the Inquisition had been established before the Renaissance, in 1231, to stamp out any questioning of the Christian Church’s authority (Fyrth and Goldsmith 1965). But opposition to questioning the prevailing mythology was not new even then. As long ago as 399 BC one of the greatest Greek thinkers, Socrates, had been ordered to either commit suicide or go into exile when he had been judged guilty of not believing in the gods in which the people believed. He was also judged guilty of corrupting young people by encouraging them to query traditional ideas, perceptions, assumptions and prejudices.

There appears to be a survival of this opposition to the questioning of mythology. For example Norman Golb (1995) has experienced huge resistance to a possible interpretation of the Dead Sea Scrolls’ significance that conflicts with traditional beliefs about the beginning of modern Judaism and Christianity. Many of us are also unable to accept what an overall look at the evidence tells us about the human settlement of the earth when it conflicts with our mythological assumptions.

Obviously, myths and legends preserve elements of what we would call history; and myth can sometimes help us understand the evidence. But in trying to fit the evidence to a particular myth, often a great deal of evidence actually discovered has to be ignored, even if unconsciously, when it conflicts with the myth. As a result usually too many inconsistencies develop. Bahn and Flenley (1992) for example point out relevant evidence Thor Heyerdahl had to ignore in relation to his theories on the Easter Islanders’ origin.

On the other hand many great discoveries have been made by people looking for evidence to support a myth and we shouldn’t hesitate to use this information.

But oral tradition or myth is not reliable as history, as we can show by many examples from New Zealand. Here are just a few. The plant tainui (Pomaderris apetala) is said to have grown from the branches used for the flooring in an early immigrant canoe of that name. In New Zealand, the plant grows naturally only in the coastal Tainui tribal district or rohe. The only other place in the world the plant is found is Tasmania. How it got to New Zealand is a mystery but if the myth is true the Tainui canoe must have come from Tasmania. I’ve never yet heard of anyone suggesting this is at all likely.

Maori myths about yet another origin canoe, the Aotea, claim the people in it brought kumara or sweet potato to New Zealand along with other plants such as karaka, cabbage tree and bracken fern, birds such as kakariki and pukeko and, in fact, everything useful to prehistoric Maori. Many of the accompanying items were obviously here long before any humans arrived. Can this story be taken as truth? On Easter Island there is a similar belief that all plants useful to the original inhabitants (including those obviously native) had been brought to the island by the first king (Bahn and Flenley 1992).

It is probable that Maori myths of canoe migrations derive from a hybrid of stories. These concern the original Polynesian arrival in New Zealand along with more recent internal migrations that had resulted from the collapse of resources within the first two or three hundred years of their arrival. All cultures have these sorts of myth. Families tend to get pushed around over time. And even within our own lifetime we get confused and often combine events in our memory that actually occurred at different times.

New Zealand Maori tradition had no memory of the extinct large flightless birds, the various moa species. Myth-believers interpret this as proving another people displaced the Moa-Hunters. It is more likely to indicate oral tradition is not actually reliable for historical events older than about 200 years.

Modern Myths

It seems we always need to have a defined beginning. The first words in the Bible are “In the beginning” and I believe that this idea continues to influence our interpretation of the evidence concerning our evolution.

Anyway, groups of people, including nations, usually evolve myths about their origins. They are very seldom the whole truth. For example “Australians are descended from convicts”, “the Japanese are a very homogeneous and distinct people” and “the United States of America was settled by people who wished to escape oppression”. New Zealand’s myth is that the European element came here to found a country that would recreate the hierarchical rural class system they perceived as already rapidly vanishing back home in England. In fact, many of our ancestors came via Australia for one reason or another but I think we might stay away from those two myths.

The Japanese people are a genetically distinct population but not because they result from a single migration into those islands. They are a unique combination that has resulted from a series of immigrants who became isolated at the extreme end of the human star’s East Asian point (and see Hammer and Horai 1995). Any ancient groups could have got there by walking as Japan was connected to the Asian mainland at times of low sea level (Clark 1969 and Cavalli-Sforza 1995).

Humans were in Japan by 30,000 to 35,000 years ago (Hammer and Horai 1995) and possibly much earlier. The first mammoth hunters arrived in the region about 30,000 years ago. I suspect their language was to eventually give rise to such languages as Na-Dene, Ket, Sino-Tibetan and even Polynesian. But language usually moves faster than genes and, in general, technology moves faster than language. The next immigrants to Japan were members of a circum-polar movement of microlithic-using people (micro – little, lithic – stone).

Their language probably gave rise to the Ainu languages, which eventually replaced any earlier ones in Japan. A subsequent expansion around the western shore of the Pacific Ocean also has a connection with Japan. This spread people from Polynesia to North America and was the product of earlier movements of genes, technology and culture. More recently, around 200 to 300 BC, the rice cultivating Yayoi people moved from Korea (Clark 1969). They probably introduced the modern Japanese language.

Each of these movements remained isolated in Japan long enough to combine with any previous populations to form a distinctive, homogeneous stabilised hybrid population before the next lot of people arrived (“Hybrid Vigour and Inbreeding” [Survival]). The most recent mixing hasn’t yet been completed, as there is still a small group of distinct Ainu people in Northern Japan, though most modern Japanese would probably have some Ainu ancestry.

This process of gene flow has been happening throughout the world since humans first appeared. In fact many evolution-deniers are more than happy to accept the human population of Egypt, for example, has changed since the pyramids were built. There has been a series of waves of invaders including Nubians, Canaanites, Libyans, Assyrians, Persians, Greeks, Turks, French and English. Almost certainly, many genes remain from the ancient population but any “original” population was presumably already the product of many waves of immigration.

Any idea there is such a thing as a “pure” race is completely ridiculous. In spite of popular ideas evolution doesn’t work like that. The concept of pure breeds in animals is also artificial. Most breeds have actually been formed from what were originally geographically isolated populations though. A pure breed is simply a product of the particular time when the studbook is closed and no other individuals are allowed into the breed.

I will avoid elaborating on the other origin myth I mentioned although I’d like to quote without further comment from Tim Flannery’s (2001) book “The Eternal Frontier”. “Pilgrims from England and the Netherlands had been contracted to establish a settlement in the New World by the Virginia Company, whose sole purpose was to profit by trade”.

See next :: Human Evolution On Trial - 'Change'

Witnesses Called

Bahn, Paul and Flenley, John (1992) Easter Island, Earth Island. Thames and Hudson, London

Cavalli-Sforza, Luigi Luca and Cavalli-Sforza, Francesco (1995) The Great Human Diasporas. Addison- Wesley

Clark, Grahame (1969) World Prehistory. Cambridge University Press, UK.

Corfield, Richard (2001) Architects of Eternity.(UK/US) Headline Book Publishing, London.

Flannery, Tim (2001) The Eternal Frontier. (UK/US) Text Publishing, Australia.

Fyrth, H. J. and Goldsmith, M. (1965) Science History and Technology Book 1. Cassell, London.

Golb, Norman (1995) Who Wrote the Dead Sea Scrolls? Michael O’Mara Books, Great Britain.

Hammer, Michael F. and Horai, Satoshi (1995) Y Chromosomal DNA Variation and the Peopling of Japan. Am. J. Hum. Genet. 56: 951-962

Sturgis, Matthew (2001) It Ain’t Necessarily So. Headline Book Publishing, London.

Swartz, Marc J. and Jordan, David K. (1980) Culture - The Anthropological Perspective. John Wiley and Sons, Canada.

Tudge, Colin (1996) The Time Before History. (UK/US) Scribner, New York.

Human Evolution on Trial - Change

2009-06-20T17:25:00.000+02:00

Human Evolution on Trial - Change

The only thing constant is change. Change may be rapid but is more usually gradual. It can also be large or small. Change leads to variety through both time and space. Changes in the rate and size of change have given rise to the phenomenon known in evolution as “punctuated equilibrium”, periods of large and rapid change separated by periods of very little change.

New Zealand

New Zealand is a young country both geologically speaking and in relation to human history. It also occupies a small space on planet earth. This combination of factors makes it a convenient place to start any examination of the past.

The jury will find the patterns we discover there have a much wider relevance than just for New Zealand or even just for modern humans though. All the patterns and ideas the defence presents here will pop up regularly during the rest of this case in favour of the defendant.

New Zealand consists of two main islands, and several smaller ones, which stretch from latitude 48° south to latitude 34° south with some small islands beyond these latitudes. Most of the country’s underlying rock, or skeleton, consists of material laid down on the sea floor between the beginning of the Permian geological period (260 million years ago) and, halfway between then and now, the end of the Jurassic (130 million years ago). Over time the material was compressed, heated and hardened by the weight of the sea, chemical reactions and heat from the earth’s core. Earth movements eventually pushed up this material and made New Zealand’s skeleton. The skeleton was then overlain with younger rock eroded off this skeleton as well as with some volcanic material.

That all this change is still going on is shown by the fact New Zealand suffers many earthquakes and has several active volcanoes. In fact Australians often call us “The Shaky Isles”. The defence will provide the jury with a short history of the earth and return to this side of things in Part III (“Time” and “Long Ago”).

New Zealand has been isolated in the southwest Pacific Ocean since the southern continent of Gondwanaland started breaking up during the Cretaceous more than 65 million years ago. The nearest continent is Australia, 2000 kilometres to the west, and much of New Zealand’s plant and animal, and especially bird, life has arrived across the ocean from there. Several bird and insect species have arrived through their own efforts even in the two hundred years since Europeans got here. But there is biological evidence of ancient island connections to the northwest, via both Lord Howe and Norfolk Islands, to New Caledonia and probably even further north (Stevens 1985).

Actually some of our birds and especially plants have been here since the ancient continent broke up. For example we share, or used to share, large flightless birds with Australia, New Guinea, Africa, Madagascar and South America. The New Zealand representatives of this group have been called “moa”. They died out as recently as five hundred years ago. Several small members of this group, the kiwis, still survive in New Zealand but they too seem to be rapidly dying out.

Destruction

The arrival of humans caused a major change in the New Zealand environment. In “Extinctions” the defence will show that this has been the pattern throughout the world. Elliot, Manighetti and Carter (2003) have produced a pollen profile that shows a permanent drop in the amount of forest tree pollen from between about 1000 and 1200 AD, the generally accepted time of Polynesian arrival. The profile does show human induced fires first occurred on the east coast of the North Island about 1500 years ago. Other evidence suggests the Polynesian rat (Rattus exulans) may have also been present in New Zealand by then. The pollen profile shows the forest then soon recovered quite significantly although not quite to its previous level.

The evidence for the presence of humans in New Zealand before a thousand years ago may indicate the arrival of all-male fishing parties lost in storms or small groups of migrants who failed to leave descendants. You will later see that the source of these migrants was presumably Western Polynesia (Fiji or Tonga) but there is actually no evidence for this other than possibly some rat nuclear DNA (King 2003). In fact mitochondrial DNA evidence from Polynesian rats now living on offshore islands around New Zealand shows they are genetically closest to those from Eastern Polynesia; the Cook and Society Islands (Lisa Matisoo-Smith quoted in Howe 2003). This suggests the evidence for their early arrival may have been misinterpreted but you saw in “Pedigrees” [Populations] that mtDNA lines can die out for one reason or another.

Although some inhabitants of New Zealand claim more ancient ancestry within the country overall the evidence doesn’t support the presence earlier than about 1200 AD of any people who left descendants. Some members of the prosecution might claim any earlier settlers in New Zealand were able to live completely in harmony with their environment and that is why we can find so little evidence for their existence. The defence will offer more evidence on the subject in “Extinctions” and show this is most unlikely. If it were so they would be the only humans in the whole history of the earth to have achieved this harmony. Of course it is possible very small numbers of earlier inhabitants survived in New Zealand but they were on their way to extinction by the time the later people arrived (possibly through inbreeding and we’ll look at this next). An increase in fire, extinction of birds, carbon dating of human artifacts and the earliest stone tool types all date to more recently than 1200 AD (McGlone et al in Sutton 1994 and King 2003).

But let’s not get carried away with how special humans are. The environment usually changes, sometimes in an extreme manner, with the arrival of any new species.

The permanent settlers who arrived in New Zealand about one thousand years ago probably maintained contacts over the whole country (Sutton 1994 and King 2003). James Belich (1996) provides a good argument that a sizeable migration reached New Zealand and it spread virtually instantly around the desirable parts of the coast. He suggests that for a people who had just travelled over the Pacific Ocean a few trips around the coast of New Zealand was nothing (and see also Bellwood 1978). The relatively sheltered East Coast provided the main trade routes, seals and moa provided abundant food and everyone was happy…

…Until the most easily exploitable resources ran out.

Increasing Population + Diminishing Resources = Strife + Selection

Studies of both prehistoric and modern hunter-gatherer groups show that life is short and women have only three or four children each (see for example Houghton 1980). But these studies are not done on populations moving into previously uninhabited regions.

The population numbers of any species usually grows to the maximum possible for the resources available. As James Burke (1978) says, in relation to humans in Medieval Europe, “When times are good the population rises, and sooner or later, it rises too far”. The population growth in New Zealand could have been very rapid with adequate food, no overcrowding and no predators. Allowing a generous 25 years per generation and women having as many as ten children, half of whom would be female, the population potentially could have reached epidemic proportions in 200 years (over three quarters of a million starting with even just one couple). Rosalind Murray-McIntosh’s research on mitochondrial DNA (quoted in Howe 2003) indicates at least seventy women arrived in New Zealand, i.e. at least 200 people.

Evidence from the teeth of skeletons shows that by about 1500 AD life in New Zealand had become more difficult. Moa, along with seal colonies on easily accessible parts of the coast, had dissappeared. The diet of prehistoric Maori changed from seal and moa meat to an increase of fern root (Houghton 1980). The culture then changed and we get fortified settlements (Howe 2003) and division into separate groups, tribes.

Tribes

The word tribalism can mean different things to different people but I suggest we say it is the grouping of humans into larger units than simply families. A tribe is therefore the largest group that any particular individual considers him or her self as belonging to. It can vary from less than two hundred up to the size of a nation. Tribes are held together by shared culture. The defence showed earlier (“Mythconceptions”) that our beliefs are part of our culture. We will return to this side of things in Part V (“Culture”). In modern society, especially cities, the tribal groups we identify with can change almost from hour to hour but until recently tribes were a more stable concept. Humans, especially infant humans, survive best, or even only, as members of a cultural group or tribe. Children accept the culture and mythconceptions of the tribe they grow up with as normal. This is just as well. Life would otherwise be too complicated for most of us to cope with. It also means culture usually changes quite slowly. But elements of it can change quite rapidly when children associate mainly with their own age group during their schooling.

Tribalism is therefore part of culture and seems often to be strengthened in response to limited resources. Tim Flannery (2001) has suggested cultural diversification and tribalism developed in North America also as a result of the depletion of resources after the initial colonisation by the ancestors of the American Indians.

We might regard tribalism as the first step on the road to speciation, the evolution of life into the reasonably discreet units we call “Species”. Many animals such as dogs, rats and especially birds display tribalism and it is a learned behaviour even there. Young birds are imprinted soon after hatching with the form, colour and song of their parents. This means they usually mate with the members of their species similar to them even though they may be quite capable of mating with others. Frank Gill (1998) has stated...

“Projected to its full conclusion, this line of thinking suggests that speciation in birds is as much a cultural phenomenon as it is a genetic phenomenon”. Behaviours that lead to speciation (or tribalism) are called “isolating mechanisms” and many behavioural characteristics are genetically inherited (Jones 2000). The whole phenomenon is much more widely spread than just among birds but they do provide interesting evidence.

Galapagos Finches

The defence suggested in “Conception” [The Chinese Drover’s Clever Dog] we should assume there is one set of biological rules for the whole of nature including humans unless it can be proved otherwise.

Throughout nature during times of plenty and when numbers are expanding the boundaries become porous. Everyone parties on. Tribalism decreases and even what have been recognised as being different species may breed together. For example two kinds of Geospiza, or ground finch, from a single island in the Galapagos sometimes breed together in times of plenty (Weiner 1995). Normally the different kinds specialise in exploiting different elements of the environment. Some have a large beak and others have a small beak depending on what food they specialise in. The finches, taken together, form a double bell curve for this characteristic. Breeding is usually confined within each of the two types, big beaks breeding only with big beaks for example. Hybrids are at a disadvantage compared to the specialists. This has led to the development of two apparently separate kinds or species. But when the environment changes dramatically, such as during El Niños when rainfall increases, population numbers increase rapidly and the two separate species of finch often breed together. Hybrid individuals with middle-sized, unspecialised beaks are able to survive and breed. The two bell curves tend to merge. Genes swap between the two kinds. With the return of difficult conditions the types separate again each specialising in their particular ecological extreme. It seems that in general specialisation, tribalism and separation are greatest at times of environmental stress.

Interestingly, a similar thing has been shown to happen with human society. As long ago as 1915 John Dewey (1966) claimed different classes and social groups mix with each other more during expansive economic periods. Presumably he agreed they tend to become isolated when times are difficult. And in his book “Mapping Human History” Steve Olson (2002) claims immigrants to France over the last fifty years have been assimilated into French society more effectively during times of better economic performance. The balance of nature is very complex and constantly changing. The defence will return to this idea many times during this case in favour of Human Evolution.

It is possible that at times during human existence we have not been tribal. The numbers able to survive the worst of times determines the numbers of any particular species in any region. The human population may have been kept in check by seasonal or periodic food shortages, predators, environmental disasters such as floods, droughts etc. and even genetic diseases. It might have been a major and happy occasion when one family group met another during times of plenty. It is probably fair to say much gene flow would have occurred. The evidence indicates that throughout history the introduction of new technology has led to times of plenty. Times of plenty promote population expansion and (at least to some extent) the breaking down of tribal barriers.

But during the last few thousand years for most of us our greatest enemy has usually been each other. As resources become fewer creatures divide into closed groups. With hard times the Maori of New Zealand eventually grouped into tribes (King 2003). These tribes may have developed from divisions going back to the arrival of different canoes during the original migration to New Zealand, as oral tradition states, but to consider different tribes or “Iwi” were discrete, genetically isolated, populations is wrong. Maori myth is full of stories about people moving to live somewhere else. Much inter-Iwi marriage (pdf) occurred, especially in the upper classes. Regional differences did develop, though, and some people may be referred to as looking typically Tainui or Ngapuhi etc, though these differences are little more than family resemblances. It is also possible to tell where a native speaker of Maori comes from by their dialect and most of us are aware of the regional dialects of Britain and Ireland.

Variation Through Space

Different tribes or Iwi are actually the result of geography.

Of course throughout the world families living close to each other have always bred together and formed alliances based on common ancestry, sometimes mythical. Geographic boundaries isolate groups. Mountain ranges, especially heavily forested ones, or large swamps, isolated the various populations within New Zealand. They provided boundaries for the various tribal districts or “rohe”. For example Ngati Wai are from Northland’s East Coast. The heavily forested Puhipuhi hills and the Hikurangi Swamp separate them from Ngati Hine. The Tutamoe Range and Waipoua Forest separate Ngapuhi from Ngati Whatua (if Te Roroa are considered to be part of Ngati Whatua) though they come into contact around the south head of the Hokianga Harbour. Ngati Kahungunu are isolated by the Ruahine and Tararua Ranges and so on. You will later see the boundaries between many species are also geographic.

Variety, or difference, is a product of change through time and space and is not just confined to biology. It is even demonstrated by basic economics. The rich get richer and the poor get poorer. This used to be justified by the expression “survival of the fittest”; a term first used in 1852 by Herbert Spencer while he was sub-editor of the paper “The Economist”. In economics the concept obviously leads automatically to monopolies but most economists still prefer to keep quiet about that (Saul 2006).

The passing of time leads to greater change and so to greater variety. But Maori may not have lived in New Zealand long enough, or the country may not have been large enough for them to develop into tribes of the American Indian type. For example a single Maori language was spoken throughout New Zealand (King 2003) but the pre-European population of America shows a much greater level of variety. Apart from those of the far northwest, most languages of the American Indians are possibly related to each other and may have an ancient common origin (Greenberg and Ruhlen 1992). But subsequent internal migrations mean that individual tribes do not always understand their neighbours’ languages.

Africa provides an example of even greater variety of population. When I travelled in West Africa I could generally tell whether a person was Wolof or Mandinka by their features and the sound of the language even though I couldn’t actually understand either language. This is more than I can do for most national groups in Europe, but humans are presumed to have been in Africa longer than anywhere else and so differences have had longer to develop.

You will find throughout this case that languages, beliefs, species, and even individual genes, have all separated into regional varieties as they have spread around the world (for example “Pacific Population” [Mixing], “Culture” [Evolution of a Religion], “Species” [Difference], and “MtEve”[The Trees]).

Variation Through Time

Most Iwi or tribes in New Zealand trace their ancestry back to a particular individual. And so they are more like Scottish clans than they are like American Indian or African tribes. It is probably no accident groupings of Maori families or “Hapu” are referred to as Iwi. Iwi also means bones. Hapu (clan) means pregnant. While we’re on that subject whenua, land, also means placenta.

A claim to have descended from a particular ancestor usually gives an individual the right to live in a particular district or rohe. Sometimes it is suggested burial rituals in human culture may have first developed from a desire for descendents to stake a claim to a particular territory (Cunliffe 1994). As early as late “Middle Paleolithic” (paleao – old) Neanderthal times (about 40,000 years ago) there is controversial evidence for ritual burial (D’Errico 2003). But with the development of larger populations and the diversification of cultures during the “Upper Palaeolithic”, from about 35,000 years ago, the evidence is definite. Before this time human groups may have been more mobile.

But we can classify humans into a hierarchy of divisions or groups depending on the closeness of relationship, each level containing progressively more members. These groups make up a continuum. As in a pedigree numbers increase as you move to the right.

Individual / Family / Whanau / Hapu / Clan / Iwi / Tribe.

Membership of divisions further to the right indicates a more ancient common ancestry, progressively more likely to be based on mythconceptions.

Genetic similarities can be used to indicate close relationships at the left-hand end but beyond the right hand end, and often before then, genetic differences become regional rather than tribal. For example, as you saw in “The Human Star” [A Cline], the main genetic difference within the people of Europe shows up as a simple genetic gradient or cline from the northwest to the southeast despite the complicated distribution of different races and language groups (Cavalli-Sforza 1995). Even within North America and Australia the main gene variation of the pre-European inhabitants forms a cline and the various tribes cannot be distinguished genetically. Breeding is usually between near neighbours, or at least it was before the development of modern transport such as aircraft and even the bicycle.

The defence will now show the jury a diagram of these connections from the opposite point of view. It is like an individual’s family tree. The various lines all reach the bottom of the diagram but this would be very difficult to show.

Because languages change over time they too display degrees of separation. They evolve. The English language has actually changed considerably even in the short time since I was a child. It has taken on new words and expressions and many words have changed their meaning. The wave theory of genetic, cultural and technological evolution tells us that languages expand as waves. Although they usually mix with other languages they can also be arranged in the form of a family tree. We’ll later use this idea to help us follow human migration. The defence will even argue that genes spread in much the same way languages do, but by no means always together.

The evolution of languages can also tell us about evolution in general. Regional or spatial language variations start to develop with dialect being the first, grading in time to differentiation into separate languages within a particular language family. It can be very difficult to define the boundary between languages within a group though. For example the people on different islands in Polynesia speak different dialects and speakers of some dialects cannot understand some other dialects. The relationship is not simple as Rarotongans can usually understand much of New Zealand Maori but changes in the languages make it very difficult for some speakers of Maori to understand Cook Islanders. The relationship between species is not simple either, as the defence will later show.

The language we speak is part of our culture. Culture, including language, myths, clothing, art, music, sport and religious beliefs can serve to unite groups (even different tribes or races) and can promote gene flow.

But culture can also divide groups and obstruct gene flow. It usually relies on accentuating exclusiveness and division, a “them and us” philosophy. (Gene flow usually occurs even in this situation though). In other words culture can lead to differences that are apparent rather than real.

Culture and technology can travel further and faster than genes and there are many examples of groups adopting at least some elements of a different culture and technology. In fact New Zealand provides a good example of the mixing of two languages, two cultures, two technologies and two gene pools.

European Migration

The arrival of Europeans and the various animals and plants they brought with them led to yet another major and rapid change in New Zealand’s environment. History records that in 1642 the Dutchman Abel Tasman was the first European to see New Zealand but it is fairly likely Portuguese or Spanish sailors had already done so. It was Captain Cook’s voyage in 1769 that brought New Zealand to the attention of Europeans though. Sealing and Whaling ships soon visited and bases were established around the coast. Traders, escaped or released convicts from Australia and general adventurers then arrived followed by European missionaries. European men were readily accepted into Maori society because they brought in new technology (King 2003). Missionaries’ wives were probably the first European women to live in New Zealand but European women didn’t arrive in the country in any numbers until after 1840.

Until that time gene flow between the two human populations in New Zealand was almost entirely between European men and Maori women. In fact cultural factors meant Maori men didn’t contribute many genes to the European side of the population until long after that time. By then many Maori people already had some West European genes and spoke an imported language, English.

The English language itself is part of the German group and is a product of the Anglo-Saxon movements into England that started about 1600 years ago. This was not an instantaneous change either and it may have taken up to 300 years for English to replace any previous languages in England (Davies 2001). In fact there is a great deal of evidence to show much of the original population survived. This all goes to show that culture, including language, doesn’t necessarily coincide with chromosomes and DNA.

The defence will mention many migrations throughout this story and they should all be regarded as being similar to the movement of Europeans to New Zealand, Anglo-Saxons to England or the various groups into Egypt (“Mythconceptions” [Modern Myths]). A reasonably gradual process including mixing with the original population, usually at first by incoming males with resident females, a gradual mixing of genes and the eventual dominance of one language over the other, not always by the incoming one. Total population replacement is very rare. The movement of Europeans into New Zealand was fairly rapid because of modern transport. It was also complicated by the loss of a number of the indigenous population through internal wars, introduced diseases and the Victorian cultural attitudes of the immigrants.

New Zealand provides useful evidence for the defence case. We have at least two groups who can definitely be called different races with different cultures who are mixing genetically. One language is replacing the other, although words from the original language are being adopted by the more recent arrivals. International communications in one of these languages is hindering this exchange and during prehistoric times the whole process may have been more balanced. Languages too are able to form hybrids. Mixed languages are called “Creoles” but usually just one language dominates and it simply borrows words from the other (Jobling et al 2004). Any combined language always uses at least the basic elements of just one of the parent languages. Languages are classified by examining these basic elements because individual words can zoom around the world.

Today most New Zealanders have genes from a variety of ancestors; Ngapuhi, Ngati Wai, Wai Taha, Scottish, English, Chinese, Pacific Islanders etc. and what we can call Dalmatians or South Slav. In other words a mixed gene pool. The jury will eventually see it had been this way with their ancestors even before they left wherever it was they left to come here. But if somehow New Zealand became isolated for many generations, or several hundred years, the mix would eventually produce a new race with a new culture and language. Within that race people in the northern and eastern regions of the North Island would tend to have darker skin compared to those in the South Island.

They will have a higher proportion of Polynesian genes. Some Y-chromosme and mitochondrlal DNA lines will have died out but the majority of surviving lines would probably descend from European ones. Remember that in just 250 years time each individual’s pedigree will contain a list of over one thousand people alive today.

It is often said “the more things change the more they stay the same”. The defence will argue races and cultures have always developed in exactly the way New Zealanders have. In fact the pattern stretches right back to at least as far as our origin as a species. Human groups in contact with each other have always produced hybrids (crossbreeds) through gene flow. Homo erectus (“man erect” and see “First Humans”) may have been well named.

The jury will eventually see population movements have been continuous during Human Evolution. But we will need to brush up on genes before the defence can use the Polynesians’ evolution to help explain the evidence in favour of the defendant.

See next :: Human Evolution On Trial - 'Hybrid Vigour And Inbreeding'

Witnesses Called

Belich, James (1996) Making People. Penguin Press, Auckland.

Bellwood, Peter (1978) Man’s Conquest of the Pacific. Collins, Auckland.

Burke, James (1978) Connections. Macmillan, London Ltd.

Cavalli-Sforza, Luigi Luca and Cavalli-Sforza, Francesco (1995) The Great Human Diasporas. Addison- Wesley

Cunliffe, Barry ed. (1994) The Oxford Illustrated Prehistory of Europe. Oxford

University Press, Oxford.

Davies, John (2001) The Celts. Cassell and Co., U.K.

D’Errico, F. (2003) The Invisible Frontier: a Multiple species Model for the Origin of Behavioral Modernity. (pdf) Evol. Anthrop.12, 188[-202.

Dewey, John (1966) Democracy and Education. The Free Press, New York.

Elliot, M., Manighetti, B. and Carter, L. (2003) Dating the Human Colonisation of New Zealand. Proceedings of the New Zealand Geographical Society.

Flannery, Tim (2001) The Eternal Frontier. Text Publishing, Australia.

Gill, Frank B. (1998) Hybridization in Birds. (pdf) The Auk, Vol. 115 No 2 April.

Greenberg, J. and Ruhlen, M (1992) Linguistic Origins of Native Americans. Scientific

American, 267 –94-99, Munn and Co., New York.

Houghton, Phillip (1980) The First New Zealanders. Hodder and Stroughton, Auckland.

Howe, K. R. (2003) The Quest for Origins. Penguin, New Zealand

Jobling et al (2004) Human Evolutionary Genetics. Garland Science, New York.

Jones, Steve (2000) Almost Like a Whale. Anchor, London.

King, Michael (2003) The Penguin History of New Zealand. Penguin Books, New Zealand.

Olson, Steve (2002) Mapping Human History. Houghton Mifflin Company, New York.

Saul, John Ralston (2006) The Collapse of Globalism. Penguin Books, England.

Stevens, Graeme (1985) Lands in Collision. Science Information Publishing Centre,

Wellington.

Sutton, Douglas G. ed. (1994) The Origins of the First New Zealanders. Auckland University Press, New Zealand.

Weiner, Jonathan (1995) The Beak of the Finch. Random House, London.

Human Evolution on Trial - Hybrid Vigour and Inbreeding

2009-06-20T17:20:00.000+02:00

Hybrid Vigour and Inbreeding

Most of our nuclear DNA is involved with the basic things of life like development, growth, respiration, healing etc.: things we share with other life forms. This is why we share so much of our DNA, even with very simple forms of life. But we are told no two individual humans (or any other species) have exactly the same nuclear DNA. This makes each of us different. The variation in DNA is usually accepted as evidence to identify individuals in paternity or criminal cases. The difference between individuals in the human population is put at about 0.02% or so. It is the regional variations in just this 0.02% the gene maps used in my story actually represent. The difference in DNA between species is much greater. It is usually claimed humans and chimpanzees share at least 98% of their DNA (see for example Stringer and McKie 1996). Therefore the difference between these two species is as much as a hundred times greater, about 2%. The difference becomes greater still when we compare humans in turn with mice, birds, fungi, plants or bacteria.

Hybrid Vigour

In fact the pairs of chromosomes and their DNA seem to work more efficiently if they are not exactly the same as each other. Up to a point the more heterozygous “Bb” or “bB” gene combinations you get compared to the number of homozygous genes (double recessive or double dominant, bb or BB) the more you have what is called “heterosis” or “hybrid vigour”: extra fitness and ability to survive. For most species this often also means more breeding success.

Breeding success is actually a product of many factors: the act of fertilization itself, abortion during pregnancy, the death of the mother during the birth process, weak or deformed offspring, etc. For any given population it is usually possible to measure breeding success in some way but as Charles Darwin said, “for all practical purposes it is most difficult to say where perfect fertility ends and sterility begins” (Jones 2000). As the chromosomes and DNA become either more the same or more different breeding success goes down. This can be shown diagrammatically, as a bell curve.

The graph’s peak indicates hybrid vigour, at least for breeding success. I’ve shown no scale but the right hand end of the graph probably varies in the steepness of its fall for different pairs of species. The development of either genes with conflicting effects or behaviours called isolating mechanisms could lead to quite abrupt falls at the right hand side of the graph. Anyway, by 2% humans are separated from chimpanzees.

As the difference between the genes on offer at fertilization increases beyond the peak there is a progressive decrease in breeding success. The genes begin to combine poorly. Some matings between parents recognised as belonging to even separate species may be capable of producing offspring but often only one sex of the offspring is fertile, e.g. yaks and cattle, or virtually none of the offspring may be fertile, e.g. horses and donkeys (mules). But any fertile offspring are capable of transferring genes between even these species.

Any further difference and fertilization itself is not possible. The parents can definitely be called separate species. But the separations between species cover nearly the whole of the right hand side of the bell curve. The last step of separation may be completed by the reversal of parts of the chromosome or by a change in the number of chromosomes by their splitting or combining. For example chimpanzees have an extra pair of chromosomes as compared to humans. Chromosome 2 in humans seems to be a combination of two chromosomes possessed by a common ancestor (Ridley 2000). It seems that neither of these changes is as definitive as appears at first glance though.

Even within a species some individuals may have parts of a chromosome reversed, and Stringer and McKie (1996) remark that many humans have chromosomes with bits missing (deletions) or added in (repetitions). They add these variations usually have “no bearing on a person’s genetic well-being”. And some hybrids of species with different chromosome numbers can be perfectly fertile. For example the Asian wild horse (Przewalskii’s horse) has 33 pairs of chromosomes but has no trouble forming fertile hybrids with the domestic horse which has 32 pairs. Also horses and donkeys have different chromosome numbers but the hybrid offspring are not always sterile. Besides many different species within a group may actually have the same number of chromosomes.

Rather than being the result of a different number of chromosomes, the lack of fertility between species appears to come about through differences in what is on those chromosomes, the genes responsible for turning on or off other genes. Genes with conflicting effects can prevent the survival or even formation of the foetus (Jones 2000). Of course if just one individual within any population has a mutated incompatible gene it is impossible he or she could leave any offspring. For a single population to develop into two separate species with mutually incompatible genes each species would have to develop by the accumulation of many small genetic changes over many generations. Speciation, the development of two separate species or kinds from one, is therefore usually gradual.

Now, if we go back to look at the other extreme we find that as the parents become genetically closer breeding success can also become close to, or actually, zero for many species. This is called inbreeding depression.

Inbreeding

The bell curve’s left-hand end represents inbreeding depression or loss of heterosis. In a population of fixed size genes will be eliminated over generations either randomly or by selection. The opportunity for two different genes to meet is gradually reduced. With less opportunity for variation the members of a population become more similar to each other over time, both genetically and in appearance, and the level of heterosis falls.

It is most likely each one of us carry one or more genes that would be lethal if we had a double dose (Steve Jones 2000). Because of this it has been suggested a human population of less than 400 to 600 is not viable in the long term (Rhys Jones quoted in Flood 1988). Interestingly this seems to be the average size of tribes of hunter-gatherers (Cavalli-Sforza 1995). This fact also has implications for the preservation of threatened species (Tudge 1996). Of course if intense selection within a population has already eliminated any lethal genes inbreeding is not a problem.

But more usually as the level of inbreeding increases the chance of two of these lethal (or at least disadvantageous) recessive genes coming together is greatly increased. Any dominant gene useful for survival is usually already widely spread. Any recessive gene that confers an advantage has also usually already replaced any other gene and so inbreeding usually brings out recessive genes that limit survival and breeding success. Inbreeding can be a big problem for animal breeders. Most breeds by definition have a fairly limited genetic variety to start with.

Many people involved in dairy cattle breeding are worried about inbreeding. The use of artificial insemination for many generations has meant the world’s dairy herds are becoming more closely related through the continued breeding to the best bulls available. This has already resulted in a loss of fertility in the international dairy herd, although selection only for production at the expense of fertility has probably been the main factor in this case.

The human genome is well studied and I guess we know as much about human genes as any genes. But for the study of population genetics the national dairy herd can’t be beaten. The ancestry of 85% of the New Zealand herd is on computer. When the technician arrives to inseminate a cow it is possible in many cases to tell what the theoretical loss of production through inbreeding for that particular combination of bull and cow will be.

This level of information is not readily available for humans. Several genes have been discovered in cattle that lead to the death of the foetus if it finishes up with a double recessive. In many cases the mutation that causes this has been traced through breeding records to the individual animal that introduced it to the New Zealand dairy herd. This is often also the individual in which the mutation occurred.

When two inbred populations meet, mix and breed some level of heterosis is restored in their offspring. This is called hybrid vigour. D. S. Falconer (1964) says, “the phenomenon of heterosis is simply inbreeding depression in reverse”.

Wave Theory of Evolution

Large stable populations are, by definition, successful and largely in balance with their environment. Selection is therefore towards the average for that population. The bell curve for any characteristic is steep on either side. But individuals can carry a recessive gene that doesn’t show up in the individual’s observed characteristics. Half the offspring of any individual with a mutated gene will, on average, carry that gene. Any new gene that forms through mutation may become widely dispersed but unable to form a double recessive, and so subject to selection either for or against, for many generations. A double recessive will only be possible when two individuals with the recessive gene are themselves able to mate and produce offspring. Therefore double recessives usually come about through inbreeding. On average one quarter of the offspring of two single recessive parents will be double recessive and express the genotype.

Of course if individuals with the double recessive are at a disadvantage selection will keep the gene at a low level. Otherwise these double recessive individuals will occasionally meet and mate with other individuals in the population that have the single recessive mutation. This time half their offspring will be double recessive. Selection for or against the mutation can then get seriously underway. If individuals with the double recessive leave many more descendants the change in the population could be very rapid as the gene spreads through a population containing many single recessives. The bell curve will widen, flatten out and then shift its centre.

The species or sub-species most different to the rest of their kind (including other species in the genus) are usually found at the geographic extremities of the range of that collection of species. As I mentioned in “The Human Star” [A Map] this fact has been recognised for a long time (Mayr and Diamond 2001). Environmental conditions at the geographical extremities of a population’s distribution are more likely to be marginal for the survival of that population leading to smaller numbers and isolation. This increases the likelihood of either extinction or selection in a particular direction through inbreeding. Genetic mutations in the central area of the distribution may also either fail to reach the margins or become subject to selection only once they do.

The fact that chromosomes and DNA are subject to change means populations of a species that have become genetically isolated or had different selection pressures acting on them will develop a different gene pool and usually appearance. Any species, including the human species, which inhabits a large geographical area, varies over that area. As an extreme example Tim Flannery (2001) mentions the grizzly bear of North America. It was at one time divided into a ridiculous seventy-four different species.

These species actually show much less physical variation than do the different modern breeds of dog though, presumably all descended from a single species of wolf. The different kinds of the many species of animals, birds and plants that vary markedly over their range are usually quite capable of forming fertile hybrids when brought together. The kinds are similar to human “races”.

But sometimes even what are definitely recognised as being separate kinds or species show what are called “hybrid zones”, regions where a proportion of the individuals have a mix of characteristics of the two species. Occasionally the hybrid population has been classified as a third species until the mistake has been realised (Gill 1998). Hybrid zones between pairs of species are usually narrow because of selection against the hybrids. If the hybrid zone is wide it means genes flow freely between the populations. The two types grade gradually into each other and they form a cline, a series of subspecies.

A new characteristic in a species could arise, and probably usually does, through inbreeding in an isolated population (Tudge 1996). Isolation is probably usually geographic but it can be tribal. Again the development of any new characteristic may lead to recognition of a separate subspecies. But if there are not many individuals in any particular population its survival will depend on contact with another group before the inbred population becomes extinct.

If some new characteristic in an inbred population is advantageous to the species as a whole the genes will be able to spread into any incoming population by selection in the hybrid zone. A hybrid zone of just one fertile hybrid individual is sufficient to transfer genes of course. In some cases the incoming group may be inbred as well. The spread of the characteristic could then be helped by restoration of heterosis in hybrids between the inbred population and the incoming group.

I have just pointed out that individuals with a single recessive gene could become widely but thinly spread in a population before selection begins to operate on double recessives. It has probably been the sudden expansion of recessive genes that has led to the pattern of sudden change observed in the fossil record called “punctuated equilibrium” (Tattersall and Schwartz 2000). The balance of nature is very fluid and so are the hybrid zones (Gill 1998).

Survival

Extinction or survival is a function of the numbers in the population. This is often a function of the size of the area available to it. Rises in sea level at the end of ice ages resulted in a reduction of the size of islands in most places. The consequent drop in population numbers leading to inbreeding and local extinction has been offered as an explanation for the gaps in the distribution of many bird species through the islands of Northern Melanesia (Mayr and Diamond 2001). There has also been differential extinction of tigers, elephants, rhinoceros and orangutans through Island Southeast Asia with rising sea level. The same thing seems to have happened with humans in that region in prehistoric times.

In fact reduction in the size of individuals often occurs in populations confined to areas of limited extent such as islands (Tudge 1996). The Shetland Islands, north of Scotland, provide a well-known example in the popular Shetland pony although it may be a product of human breeding. But there are other examples from other islands. Smaller size means individuals use fewer resources therefore more numbers can occupy the same space (Jones 2000). This makes inbreeding less likely. If an isolated population is able to reduce the size of individuals rapidly enough, it will survive.

Human induced changes in animal breeds is usually achieved by inbreeding, called “line breeding” when it is done in a controlled manner. Change in a breed’s body size, shape or colour can be very rapid when this method is used. But reducing population numbers through intense selection also leads to problems with inbreeding.

Change can also be rapid in nature (Tudge 1996). Ernst Mayr and Jared Diamond (2001) point out that several bird species that can have re-occupied Long Island in Northern Melanesia only since a volcanic eruption destroyed life there in the seventeenth century have already begun to differentiate from the nearby populations that are presumably their ancestors. They provide three explanations for this: they are “character displacement”, “founder effect” and “formation of a stabilised hybrid”. “Character displacement” results from the same process as human breeding of domestic animals, the changing of a characteristic through selection in a particular direction.

Change in the environment leads to the same effect in nature. The process has led to pesticide resistance in insects and anti-biotic resistance in bacteria. The “founder effect” is a special case of genetic drift. It happens when a new population doesn’t contain a completely representative sample of genes from the original population. Because the new population starts off with a different mixture of genes it is slightly different right from its origin.

This is one of the random elements in evolution. Lastly “formation of a stabilised hybrid” means the establishment of a species that combines characteristics from two other populations. Farmers find that, apart from the first generation, hybrid populations of any given pair of cattle breeds for example are very variable. In the first cross recessive genes from either breed can be obscured by dominant genes from the other and so all the first hybrids tend to look much the same.

Commercial breeders use this to advantage. New double recessive combinations are able to form only once the hybrids themselves are able to breed with each other. It is only after several more generations of breeding and selection within the hybrids that the characteristics stabilise again and the extremes are eliminated. Again, the same process happens in nature. In fact the above three methods of genetic change have all happened during our species’ evolution.

For example it’s almost certain that many times during our history groups of humans with a new technology have advanced through territory already occupied by other humans, often of quite different appearance and sometimes even classified as being different species. The advancing wave would be unlikely to contain a totally representative sampling of genes from any original population and so would demonstrate the founder effect.

As the group advanced through different environments it would have undergone character displacement and eventually would consist of small, inbred groups. They could then have formed hybrid populations with any resident inbred groups they encountered. Over generations the members of the combined population would have become more similar to each other as genes were eliminated. They could then be called a stabilised hybrid.

Inbreeding in a small isolated population can be offset if there is still a degree of genetic variation within it and, through the availability of unlimited resources, the population is suddenly able to breed up very rapidly. This shuffles the genetic variability available into as many different combinations as possible. This can happen when members of a species are able to use a so far unexploited region and selection is minimal. If some inbred population were suddenly able to expand into a new region or use the old region in a new way it could lead to the apparent sudden appearance of a new species.

A rapid buildup of population may have occurred at times during our prehistory, e.g. in the Pacific islands, the Americas, Australia and perhaps other areas in even earlier times. Possibly even during the original expansion of humans. It has certainly happened with human introductions of some animals into new environments around the world, e.g. the rabbit, starling and sparrow. In general, though, studies have shown any introduced populations of less than a hundred fails to survive (Jones 2000). The case of the Chatham Island black robin may appear at first sight to contradict this argument. It has been able to increase in numbers from a single female and five males but this has involved very intensive breeding management by humans.

Usually a population can stave off inbreeding depression only if it is large enough so that the rate of elimination of genetic diversity through inbreeding is offset by the rate of mutation in the DNA of that population. Theories that new species (or new races) usually arise from the expansion of very small populations are therefore flawed.

See next :: 'Eastern Polynesia'

References

Cavalli-Sforza, Luigi Luca and Cavalli-Sforza, Francesco (1995) The Great Human Diasporas. Addison- Wesley

Falconer, D. S. (1964) Quantitative Genetics. Oliver and Boyd Ltd., Great Britain.

Flannery, Tim (2001) The Eternal Frontier. Text Publishing, Australia.

Flood, Josephine (1988) Archaeology of the Dreamtime. Collins, Australia.

Gill, Frank B. (1998) Hybridization in Birds. The Auk, Vol. 115 No 2 April.

Jones, Steve (2000) Almost Like a Whale. Anchor, London.

Mayr, Ernst and Diamond, Jared (2001) The Birds of Northern Melanesia. Oxford University Press, New York.

Ridley, Matt (2000) Genome. Harper Collins, New York.

Stringer, Christopher and McKie, Robin (1996) African Exodus. Random House, UK.

Tattersall, Ian and Schartz, Jeffrey H. (2000) Extinct Humans. Westview Press, New York

Tudge, Colin (1996) The Time Before History. Scribner, New York.

Human Evolution On Trial - 'Eastern Polynesia'

2009-06-20T17:15:00.000+02:00

Human Evolution On Trial - Eastern Polynesia

The New Zealand Maori language is classified as part of the Eastern Polynesian group. Eastern Polynesian languages are spoken on most islands across the central Pacific, from Hawai‘i in the north, Easter Island in the southeast to New Zealand in the southwest (map 3). All the languages within the triangle are quite closely related and have probably diversified only in the last 1500 years or so. The defence claims we can use the Polynesians’ expansion into this previously uninhabited region of the earth to explain several ancient examples of human migration, and our evolution.

The Polynesian group, as a whole, includes Western Polynesian: Tongan, Samoan and some other related languages, both nearby and far to the west. The Far Western Polynesian languages are called the “Polynesian Outliers”. These are generally accepted as the product of movement west from the central Pacific. The Polynesian Outliers are scattered through parts of Eastern Melanesia: New Caledonia, Vanuatu and the Southern Solomon Islands. Most of the Melanesian languages are not Polynesian although many are related to it. We’ll come back to this next in “Polynesian Origins” [Language Families].

Fiji lies on the boundary between Polynesia and Melanesia. Some linguists consider the Fijian languages to be the closest to ancestral, or proto, Polynesian (Jennings 1979). We’ll come back to how the Polynesians’ ancestors reached Fiji in “Pacific Population” [Lapita]. It is difficult to know whether Samoa or Tonga were the first islands settled after Fiji. Both groups share with Fiji quite a common cultural heritage, and quite a movement from Tonga back to Fiji occurred even in historic times (Howe 1984). In Polynesian languages “Tonga” means “south”, “Tokelau” (tokerau in Maori) means “north”, “Tongareva” (rewa) may mean “float south”, “Tahiti” (tawhiti) means “distant” and “Tuamotu” may mean “islands beyond”. The defence suggests these names are significant for the study of Eastern Polynesia’s settlement.

Polynesian Languages

Comparison of language relationships, cultural variation and physical similarities produce the following diagram (Houghton 1980, and Jennings 1979). The dotted lines enclose the cultural groupings within Polynesia. Apart from New Zealand and the Chatham Islands, which are actually south of Fiji, the islands are in about their geographic positions (see map 3). The names by which the cultural groups are known appear in Italics and are underlined. The solid lines show language connections, the numbers the presumed place of development of language types.

Polynesian Evolutionary Tree

The place of branching for 1, 2, 3 and 4 is fairly obviously in the stretch of islands between Tonga and Tokelau: South and North. Interestingly the island of Western Samoa is actually called Savai‘i, the same word in their dialect as the Maori place of origin: Hawaiki. Some of the languages spoken through the Northern Cook Islands, part of the Intermediate region, may branch off in the gap between proto-Nuclear Polynesian and proto-Central East Polynesian (Jennings 1979), which makes sense.

The earliest adzes in the Marquesas Islands resemble ones of the same age (about 2000 years) on Samoa (Bellwood 1978) and so it is generally accepted the people of Eastern Polynesia came from near Samoa. But the order in which the islands were settled and the place of development of the distinctive Eastern Polynesian culture are disputed. There are difficulties in accepting as candidates for the development of this culture any of the relatively large islands such as Hawai‘i, the Marquesas Islands, or Tahiti in the Society Islands.

A dispersal centre for Eastern Polynesians at 5 would eliminate all the contradictions (such as unexplainable patterns of change in culture and fishhook styles) introduced by placing it at any island group actually named in the diagram. Number 5 covers the islands of Tongareva, Rakahanga, Manihiki, Pukapuka and the Phoenix and Line Islands. Many of these small islands were uninhabited when Europeans first reached them but most showed signs of having been inhabited at some time. None are large enough on their own to be a centre for the development of Polynesian culture. But I would like to suggest each single coral atoll could have supported a large population for two or three generations, by which time another island would have been discovered and off they would all go again. I understand dog remains have been found in the Northern Cook Islands dated to about the right time to support the idea of this migration route.

Islands

McGlone et al (in Sutton 1994) call finding previously unoccupied islands the prehistoric equivalent of winning a lottery. With huge populations of birds and animals with no fear of humans, and undisturbed fish and shellfish in the surrounding sea, there would have been no shortage of food for these first arrivals. The huge populations of foraging seabirds would also have made unoccupied islands effectively bigger targets and easier to find than they would be today. Any volcanic islands would be sources of stone for tools, implying a great deal of deliberate two way voyaging. The whole process provides easily enough time for the culture to diverge from Samoan and become recognisably different and diversified by the time the Marquesas, Society (Tahiti) and Hawai‘ian islands were settled. In Part IV the defence will suggest that several early human expansions through open grassland containing scattered clumps of trees were similar.

The defence will later show that the pattern of animal “Extinctions” [What Have We Done?] can be used to date human expansion. But the lack of evidence of extinctions in the Pacific islands, apart from New Zealand (“Change” [Destruction]), is more a result of a lack of research than that it didn’t happen. There is evidence of extinctions in New Caledonia, Hawai‘i and Fiji but these are the only islands where such study has been done. Even then only Hawai‘i and New Caledonia have been well studied and they show many extinctions occurring at the expected time. The Polynesian rat also gets to all the islands at the expected time with an apparently early date for New Zealand. People were just beginning to move beyond Western Polynesia at the time the rat appeared in New Zealand (some time between 300 BC and 300 AD). You saw in “Change” [Destruction] there is also evidence of man-induced fires in the eastern North Island this early (Elliot, Manighetti and Carter, 2003).

The ancestors of the Maori didn’t actually arrive in New Zealand and the Chatham Islands direct from the Northern Cook Islands, or the area of number 5. Of course my diagram is a bit simplified. There is quite a bit of evidence, such as the types of stone tools found in each region dating to the appropriate time, that the first settlers actually came to New Zealand mainly via the Southern Cook and Austral Islands (Sutton 1994). The recent arrival in New Zealand of people from Tonga and Samoa represents the opening of a new migration route. There is really no evidence any migration direct from that region contributed to the prehistoric population of New Zealand, but it is not impossible.

David Tuggle (Jennings 1979) postulates the settlement pattern for Hawai‘i was the same as that suggested by James Belich (1996) for New Zealand: a dispersal of people around the most easily exploitable regions at the first colonisation (“Change” [Destruction]). Population growth eventually pushed people into less desirable locations. This was probably the pattern on all the islands and certainly seems so on the Marquesas (Howe 1984). All human migrations into uninhabited regions, including very ancient ones (see “The First Point” [Homo habilis]), have probably been similar. The rapidly advancing wave lives off the easy pickings. People left behind, or coming in following waves, have to adjust to fewer resources. Sometimes those left behind have even become extinct and disappeared entirely.

I believe it may have been during the first stage of movement into the Pacific Ocean beyond Western Polynesia that the legends of the hero Maui fishing up islands (discovering them?) developed. More islands kept appearing ahead of the migration wave and, by human assumptions or Chinese drover’s clever dog syndrome, someone must have made them or brought them up. It was handy if, in the future, you could claim your ancestors had been on the island when Maui fished it up though.

Study of the distribution of Polynesian myths could be revealing. For example it would be interesting to know if the name Kupe is confined to New Zealand. We do know the islands of the Marquesas and Mangareva have a similar hero named Tupa (Orbell quoted by McGlone et al in Sutton 1994). Therefore Kupe is possibly a general name for an explorer; in other words any great sailor was given the name “Kupe.” So Kupe could represent a string of people given the same name because they had the same attributes, as probably does Maui. The defence will suggest some other examples from oral tradition in “Culture” [Evolution of a Religion].

Marginal Polynesia

Loss of genetic variation during their evolution means Polynesians from the many different islands are remarkably similar to each other. I met native Hawai‘ians in a bar in Arkansas, USA. The Hawai‘ians looked exactly like New Zealand Maori. In fact when I first entered the bar I thought, for a while, I’d been magically transported to some bar in New Zealand.

The Polynesians are known as a large-framed people (Houghton 1980). This large frame is an unusual characteristic for both tropical and island populations. Generally speaking creatures in tropical regions tend to be smaller, or at least thinner, than are their relations in cooler areas. This is called “Bergmann’s rule” (Stringer and Gamble 1993). We saw in “Hybrid Vigour and Inbreeding” [Survival] it is also a general rule that creatures that are large on a mainland tend to be smaller on islands (Malcolm Browne in Wade 2001). The most likely explanation for the unexpected Polynesian physical type is that cold, wet nights, especially those spent at sea during migrations or fishing expeditions, would favour the survival of individuals with a larger body mass (Howe 2003). Smaller people lose heat much more rapidly and would suffer hypothermia. Movement between islands within Polynesia also offset the usual tendency for creatures on islands to become smaller. In other words the populations were not actually confined to single small islands. This would also help counter inbreeding.

Physical features of the people of each island group are closest to those of their nearest neighbours. This means there is basically a gradient of variation from the widespread islands of marginal Polynesia all the way back to Western Melanesia, a cline. Even where it is obvious there has been a movement back into Melanesia by Polynesian-speaking people originating from the area within the above diagram (Howe 1984) the cline is maintained. These people have now become genetically mixed with their neighbours (Melanesian people) but maintain their Polynesian language (the Polynesian Outliers).

But at the eastern end of the cline populations of the various widespread groups of islands are more similar to each other than they are to their nearest neighbours in the Central region. This doesn’t prove movement around the edge but suggests the lines in the diagram don’t represent single migrations. Kazumichi Katayama (Sutton 1994) shows that people from the Southern Cook Islands are as similar to Samoans as they are to New Zealanders. This indicates there were a series of genetic movements or waves along the old routes. In fact both genetic and linguistic evidence supports the idea of a series of movements along the lines.

Tracing changes in the languages shows the marginal area generally preserves older versions of the ancestral language but innovations in the Central area have spread unevenly into the marginal regions. In fact the innovations appear not to have reached Easter Island at all. That language preserved elements of Western Polynesian languages (Bahn and Flenley 1992). In “Indo-Europeans” [Celtic] you will see a similar thing happened with the Celtic languages. Ray Harlow in Sutton (1994) suggests regional dialects spoken in New Zealand may reflect changes in the dialects spoken in the Central islands. In other words there were several movements into New Zealand from several places but probably over a short period, say 200 years at most. During the remainder of this case the defence will present many examples of linguistic, genetic, technological and even religious innovations in a central area failing to reach the margins.

Easter Island

To finish this look at Eastern Polynesia we’ll take a quick look at the extreme eastern margin of their distribution, Easter Island. It provides excellent evidence for interpreting the whole pattern of human expansion around the world. But the jury will see the Polynesians are basically part of a cline stretching all the way to Indonesians, Filipinos and Malays.

Genetic evidence shows the first people on Easter Island were from Central East Polynesia (Lewin 1999) and physical appearance, language, culture and technology all support this. They arrived on an island reasonably well forested with Sophora trees (called kowhai in New Zealand), palms and several other kinds of tree. Archaeology reveals the first settlers used the wood for canoes and dined magnificently on deep-sea fish, dolphins and turtles, as well as nesting seabirds. But by the time Europeans first saw the island no sizable trees remained and the people were no longer able to make canoes and to fish at sea (Bahn and Flenley 1992). The trees had been cleared for firewood and cultivation, and the rats Polynesians had brought with them prevented regeneration because they ate any seeds. The seabirds had also died out (Diamond 2005).

Increasing Population + Diminishing Resources = Strife + Selection

In myth the population had become divided into two warring groups: “Long Ears” and “Short Ears”. There is no evidence these groups had a separate origin other than possibly being a previous “upper class” and a “lower class” (Roberts 1989). The resulting strife, and selection, was not nice. The jury will see that, far from being the centre of a magnificent Pan-Pacific prehistoric culture as claimed by some people, they represented the last, doomed and impoverished remnant of a population movement that had come one third of the way round the earth after leaving Taiwan more than 5000 years before. The defence now needs to explain how we know they came from Taiwan.

See next :: Human Evolution on Trial - 'Polynesian Origins'

Update 10th November 2008:

See also :: lapita-voyage.org : "The first expedition following the migration route of the early Polynesians"

(Start: November 2008, Arrival: April 2009)

Witnesses Called

Bahn, Paul and Flenley, John (1992) Easter Island, Earth Island. Thames and Hudson, London

Belich, James (1996) Making People. Penguin Press, Auckland.

Bellwood, Peter (1978) Man’s Conquest of the Pacific. Collins, Auckland.

Diamond, Jared (2005) Collapse. Penguin Books, London.

Elliot, M., Manighetti, B. and Carter, L. (2003) Dating the Human Colonisation of New Zealand. Proceedings of the New Zealand Geographical Society.

Houghton, Phillip (1980) The First New Zealanders. Hodder and Stroughton, Auckland.

Howe, K. R. (1984) Where the Waves Fall. George Allen and Unwin, Australia.

Howe, K. R. (2003) The Quest for Origins. Penguin, New Zealand

Jennings, Jesse D. (1979) The Prehistory of Polynesia. Australian National University

Press, Canberra.

Lewin, Roger (1999) Patterns in Evolution. Scientific American Library, New York.

Roberts, Neil (1989) The Holocene. Basil Blackwell, Oxford.

Stringer, Christopher and Gamble, Clive (1993) In Search of the Neanderthals. Thames & Hudson, Great Britain.

Sutton, Douglas G. ed. (1994) The Origins of the First New Zealanders. Auckland University Press, New Zealand.

Tyson, Peter (2008) Gigantism And Dwarfism On Islands, Nova

Wade, Nicholas ed. (2001) The New York Times Book of Fossils and Evolution. The Lyon Press, New York.

Human Evolution on Trial - Polynesian Origins

2009-06-20T17:10:00.000+02:00

Polynesian Origins

The New Zealand Maori language is part of the Eastern Polynesian group. We can use this fact to help us understand Polynesian origins. The defence will use the Polynesian language group itself as evidence in “Eastern Polynesia” [Polynesian Languages].

Language Families Eastern Polynesian languages are spoken on most islands across the central Pacific Ocean from Hawai‘i in the north, Easter Island in the southeast and New Zealand in the southwest. All the languages within the triangle are quite closely related and have probably diversified only in the last 1500 years or so.

As well as Eastern Polynesian the Polynesian group includes Western Polynesian: Tongan, Samoan and some other related languages, both nearby and far to the west. The Far Western Polynesian languages are called the “Polynesian Outliers”. These are scattered through parts of Eastern Melanesia: New Caledonia, Vanuatu and the Southern Solomon Islands. Most of the Melanesian languages are not Polynesian although some are related to it. The Polynesian Outliers are generally accepted as resulting from a movement west of languages from the central Pacific.

Polynesian as a whole is classified in turn as part of the Austronesian language group (Houghton 1980). As well as Polynesian this group includes all the other languages spoken in Fiji, Vanuatu and New Caledonia along with most languages in the Island Southeast Asian subpoint of the human star: Malaysia, Indonesia, Micronesia and the Philippines (Howe 2003). Some languages spoken in Taiwan also belong to the Austronesian group.

Many languages spoken at the northwestern end of Melanesia (The Solomon Islands and the Bismark Archipelago) are also included in this group although most languages of Northern Melanesia are not related at all to the languages discussed here. They belong to the “Indo-Pacific” family. The Indo-Pacific family includes the languages of the Andaman Islands, most languages spoken in New Guinea and possibly the extinct Tasmanian language. We’ll return to the significance of this several times later during the case (“Pacific Population” [Hoabinhian] and “Into Australia” [Indo-Pacific and Pama-Nyungan]).

All the Austronesian languages, along with Austro-Asiatic (the languages of Kampuchea and Vietnam but also found in pockets outside these countries), Thai-Kadai (languages of Thailand, Laos and neighbouring areas) and Miao-yao (scattered through much of South China) may be related to each other. They are sometimes grouped into an Austric family of Southeast Asia and Southern China (Cavalli-Sforza 1995). All these language groups within the Austric family may be reasonably closely related to each other and share a comparatively recent common ancestry. More distantly the Austric family is considered by many to be related to the Sino-Tibetan group from Northern China and Tibet, which makes sense.

Ultimately it may even be related to the Na-Dene branch of American Indian. This branch includes the Athapascan languages (Greenberg and Ruhlen 1992). All these languages possibly descend from a single language or closely related group of languages. The languages presumably long ago expanded from just a single small region.

The defence claims we can find this region if we examine the evidence available. This exercise will help the jury understand the wave theory. Here is the language family tree. Remember Indo-Pacific is not included here. It is not related at all to these languages.

For a start linguistic evidence points to Taiwan as being the point of origin of at least the Austronesian group of languages (Bellwood 1978). Mitochondrial DNA evidence also tends to support this (Underhill et al 2001).

Genes

The study of Polynesian mitochondrial DNA (mtDNA) and Y-chromosomes conducted by a team of people from around the world including Dr. Geoff Chambers of Victoria University in Wellington, New Zealand, (Underhill et al 2001) is an example of the cooperative use of culture for the accumulation of knowledge. The scientists have shown virtually all the female lines (mtDNA) of Polynesians can be traced back to Taiwan but most male lines (Y-Chromosome) come from islands on the way out to Polynesia: Island South East Asia, New Guinea and Melanesia. This implies several things.

First that male and female lines can be different. The defence asks the jury to remember this. Gene flow between two populations has occurred. You will see that this is a fairly common occurrence. In relation to modern times Steve Olson (2002) mentions that within some groups of South Americans virtually all their Y-chromosomes are European while their mtDNA is from local Indian people. This is not at all surprising when you think about it. When we later look at ancient human migration into the Americas (“North to Alaska” [Genetic Expansion]) the mitochondrial DNA and Y-chromosome evidence will again come together convincingly.

Secondly the jury can see from this that the Polynesian languages coincide with the mtDNA line rather than with the Y-chromosome (Underhill et al 2001). Many studies show that in other parts of the world language distribution seems to have a closer relationship with male movement and the distribution of Y-chromosomes rather than with mtDNA. However, in relation to the expansion and mixing of tribal groups in Africa, Basil Davidson (1974) wrote; “it was the mothers who decided what the children spoke, not the fathers”. Mothers probably usually pass on language to their children but the language a population speaks is determined by a complex set of factors. You will see during this case that language expansion is sometimes associated with mtDNA, sometimes with the Y-chromosome, sometimes with nuclear DNA and sometimes it seems to be independent of any of these. Each individual case is different. We usually call the language we grow up with our “mother tongue” though.

Thirdly the evidence suggests the mobile population was in some way matriarchal in organisation. More adventurous males from the south may have introduced the incoming females to the islands though. Either very few women from the south joined the migration or their mtDNA died out. (I understand some recent research has found one mtDNA line in Polynesia that originates from New Guinea).

Societies

The pattern of human Y-chromosome and mitochondrial DNA distribution through most regions of the world has been interpreted as showing long distance movement of Y-chromosomes with locally more mobile female populations. In roughly 70% of modern human societies women move to live with their husband’s family (Jobling et al 2004). But there is a possibility this pattern may have developed as recently as the last few thousand years as a consequence of organised armies, especially those equipped with bronze or iron weapons (but even stone would do).

On the other hand many anthropologists believe that even in apes “it is generally females that leave, or are abducted from, their native group when they mate” (Ridley 2000).

But this may be largely a figment of male anthropologists’ wishful thinking. When we actually look at the evidence we see that although it does occur occasionally in gorilla groups there is certainly no general tendency for it to happen in chimpanzee society.

Marc Swartz and David Jordan (1980) write “chimpanzees also have a distinctly casual social grouping in which only the mother and her offspring form a stable unit in an otherwise shifting series of relations”. And Jane Goodall (1990) has written “there is no closer relationship in chimpanzee society than that between a mother and her grown daughter”. Adolescent female chimpanzees are sometimes kidnapped or wander off to join neighbouring groups when sexually receptive but permanent transfer is actually fairly exceptional. It is usually only orphans that swap groups (Goodall 1990). We also know that chimpanzee brothers tend to remain together. Even in the case of gorillas “it seems that maturing individuals are more likely to migrate when there are no breeding opportunities within the group into which they are born” (Fossey 1983).

The defence suggests it is most probable human populations have effectively behaved in much the same way for much of our history. Perhaps we still do.

Such things as Jewishness (Hammer et al 2000) and the Scottish clan you belong to are said to pass from your mother. It is interesting that in China surnames were transmitted through the female line until as recently as about 500 BC (Cavalli-Sforza et al 1994).

We’ll come back to some implications of this in “Culture” [Families] but species that travel in small herds or groups are often matriarchal. Examples of this phenomenon are found throughout the animal kingdom: red deer populations (Putman 1988), wild horses, turkeys, dolphins, elephants and lions. The herd usually consists of an old female and her female descendants with assorted male hangers-on. The males are usually from other families. This limits inbreeding (“Hybrid Vigour and Inbreeding” [Inbreeding]).

We know that the first few years are the most important for many aspects of our individual cultural development. In so-called primitive societies (and probably in most societies in earlier days) children are breast-fed until they are at least three years old. The men actually have very little to do with the young children. Many families in Western society today are in fact one-parent families (to judge from letters to newspapers we would be forgiven for thinking that in New Zealand most of them were). The single parent in these families is almost always the mother.

In the case of human groups it seems that although males (with their Y-chromosomes) may wander more, be first into a new environment, make the first hybrids with neighbouring groups and introduce or pick up new technology, it is mainly women who transmit culture from generation to generation.

Luigi Luca Cavalli-Sforza (1995) has even suggested that, to some extent, we can think of “cultural heritability”. His research shows social class is highly inherited. Children usually adopt the religion of their mother for example. This inheritance is not genetic of course. What children grow up with they accept as their “Culture”. Most cultures do have initiation rites for young men and women but these usually don’t take place until at least early adolescence. By then most social beliefs are well established in the individual.

Taiwan

Ultimately though the pattern of mtDNA lines in Polynesia may just reflect the fact that until at least some women reached an island there was obviously no possibility of establishing a population. Women whose mother or grandmother had travelled would be more likely to travel themselves but this still involves culture.

The evidence shows that a move south from Taiwan to as far as the Philippines occurred between 7000 and 5000 years ago (Bellwood 1978 and Howe 1984). Taiwan would have been isolated from the mainland since sea level rose at the end of the last ice age about 10,000 years ago. This implies that there had probably been an earlier movement of people possessing an improved boating technology into Taiwan from somewhere else.

The diagram of the diversification of the languages [Language Families] shows the Austronesian languages in Taiwan appear on two different branches. This suggests a ripple of movement, and probably transmission of technology, north from the Philippine Islands to Taiwan. The development of the improved boating technology in Island Southeast Asia was probably the result of a complicated series of population movements in the region.

These movements would not have been single migrations by single groups of people. They may have extended over hundreds, if not thousands, of years. They would have been similar to the migrations already mentioned of Europeans to New Zealand or Anglo-Saxons to England.

New technology has usually led to population expansion. In this case the new technology that allowed the migration may have been the dugout canoe. Canoes of birchbark built around a frame of branches were used in North America when Europeans first arrived there. Birchbark canoes may have been brought in with the first immigrants 10,000 to 15,000 years ago. Therefore they may have been invented that long ago. Dugout canoes may have been used in Europe as early as 7000 BC, 9000 years ago. People were able to get to some remote Mediterranean Islands by then (Attenborough 1987 and see “The Last Point”). Who knows where the dugout canoe developed? It had presumably developed early enough to provide the transport for the Austronesian-speaking people through Island Southeast Asia. But people of the “Hoabinhian” culture from mainland Southeast Asia had been using stone adzes for many years before this. We’ll follow the migration out into the Pacific Ocean and come back to the Hoabinhian (and a map of their distribution, map 5) next in “Pacific Population”. For now we’ll follow the northern line back in time.

Japan

There is a string of islands to both the northeast and to the south of Taiwan leading to either Japan or the Philippines. Some evidence suggests people went both ways. In fact there are indications many elements of the Austronesian technology were actually introduced to Island Southeast Asia from the north, direct from Japan (the extreme end of the East Asian point of the human star) rather than via the mainland (Bellwood 1978). This technology is the “microlithic” the defence mentioned in “Mythconceptions” [Modern Myths].

The Southeast Asian expansion certainly seems to have some sort of connection to Japan. I have seen a photograph of a “Late Jomon” (from 3000 to 4000 years ago) Japanese pottery figure (Clark 1969, the drawing on the right in map 4) that shows similarities to some Maori designs. It also has similarities to what are usually called “Celtic” designs. In “North to Alaska” [Later Migrations] the defence will suggest a reason for this. An example of a Jomon pot is shown at the bottom left. A couple of examples from the Siberian microlithic are included in the upper left. But any connection doesn’t show up in the genes.

The map of the third principal component of the distribution of genes in Asia from Cavalli-Sforza et al (1994) does show evidence of an expansion from around the Sea of Japan (map 4). It may have occurred at the appropriate time. Sakhalin Island is not included in Cavalli-Sforza’s map and so I have not shaded it in mine but it is reasonable to suppose that at least the southern end should be shaded. The Ryukyus are not included either.

Cavalli-Sforza’s map also shows the expansion may have moved across Central Asia as far as the Caspian Sea and Turkey. The opposite genetic extreme is split between India and the very far north of Siberia. I have not shown the Central and West Asian region in my map but I’ll come back to it in Part V (“North to Alaska” [Later Migrations]). I have drawn shoreline at times of lowered sea level although sea level rose throughout the world from about ten thousand years ago.

Unfortunately Cavalli-Sforza’s map doesn’t include Taiwan, Island Southeast Asia, the Pacific Islands or North America. Nor does only the Japanese genetic extreme show up in any of his world maps but wooden boats have been found in Japan and dated to six or seven thousand years ago.

Cavalli-Sforza (1995) has written “Between ten and fifteen thousand years ago, Japan was linked to the mainland – with Russia in the north and Korea in the south – and had its own internal sea. As a result, the area developed uniquely on the back of the sea’s fishing potential”. He goes on to say “The population five to six thousand years ago was already very large and numbered some three hundred thousand, thanks to the development of fishing techniques”.

Na-Dene

Many people have also noticed a similarity in culture between the Pacific Coast of North America and the Pacific cultures generally. Of course this could be due to some later contact. But Cavalli-Sforza (1995) says “it is possible that the Japanese expansion may be linked to one of the old stone-age or Palaeolithic migrations from eastern Asia to America”.

Some evidence does suggest the Na-Dene-speaking people may be genetically distinct from the bulk of the indigenous population of America. They certainly look more Asian (Flannery 2001). Their languages are definitely distinct. Rather than being related to the “Eurasiatic superfamily” all the other American Indian languages are related to Joseph Greenberg and Merritt Ruhlen (1992) consider them to be distantly related to the Sino-Tibetan group of languages discussed here. The defence will eventually be able to use the evidence to construct a complete language family tree (“Culture” [Languages]). From that the jury will see how the wave theory also explains the American Indians’ evolution (“North to Alaska” [Later Migrations]).

The island chains of the Kurile and Aleutian Islands provide an obvious route from Japan to North America for a sea-going people. Originally the Na-Dene may have moved into the islands and coast west of the Canadian Rocky Mountains. This region may not have been occupied at all by any mammoth hunters who had moved into North America near the end of the ice age, about 12,000 years ago. A migration through an ice-free corridor east of the Rocky Mountains would have diverted northern migrants from this coastal region. The Na-Dene people may have been in America for as long as the mammoth hunters although I have seen a time of 6200 years suggested and even 5250 (Lewin 1999). Some groups of the Na-Dene have moved further south, probably as recently as 1000 years ago. They have given rise to the Navaho and Apache people (Olson 2002).

I suggest the Na-Dene people of northwest North America may be part of the same population expansion that gave rise to the Polynesians. They are simply opposite ends of a cline. This would mean that all the languages in the earlier diagram could be derived from a group of languages spoken around the Sea of Japan. Perhaps as recently as 5000 or as long ago as 15,000 years. The Japanese today speak a language that is part of a different, huge language group called “Eurasiatic”. It was almost certainly introduced from Korea only about two and a half thousand years ago. The Ainu language of Northern Japan is also usually classified as Eurasiatic. I would suggest it had been introduced earlier along with the microlithic technology. The defence will show in Part V that the microlithic has connections to the ancestors of the European side of the New Zealand family as well. In other words it is possible the two main groups in New Zealand today developed at opposite ends of an ancient widespread cline. The microlithic technology must have arrived in Japan before the language though because the expansion that gave rise to the Na-Dene and Polynesians must have started before the Ainu language had become established. As the defence said before, it is usually wandering males who introduce technology.

So the Polynesians probably developed as part of a whole complex of population movements around the western margin of the Pacific Ocean from about 10,000 years ago, the end of the ice age. We’ll now return and follow the southern line’s movement into the Pacific Ocean.

See next :: Human Evolution On Trial - Pacific Population

Witnesses Called

Attenborough, David (1987) The First Eden. Guild, London.

Bellwood, Peter (1978) Man’s Conquest of the Pacific. Collins, Auckland.

Cavalli-Sforza, Luigi Luca, Menozzi, Paolo and Piazzi, Alberto (1994) The History and Geography of Human Genes. Princeton University Press, New Jersey.

Cavalli-Sforza, Luigi Luca and Cavalli-Sforza, Francesco (1995) The Great Human Diasporas. Addison- Wesley

Clark, Grahame (1969) World Prehistory. Cambridge University Press, UK.

Davidson, Basil (1974) Africa in History. Paladin, UK.

Flannery, Tim (2001) The Eternal Frontier. (UK/US) Text Publishing, Australia.

Fossey, Dian (1983) Gorillas in the Mist. Penguin, England.

Goodall, Jane (1990) Through a Window. Houghton Mifflin Company, Boston.

Greenberg, J. and Ruhlen, M (1992) Linguistic Origins of Native Americans. Scientific

American, 267 –94-99, Munn and Co., New York.

Hammer et al (2000) Jewish and Middle Eastern Non-Jewish Populations Share a Pool of Y-chromosome Haplotypes. Proc. Natl. Acad. Sci. Vol.97 pp. 6769-6774.

Houghton, Phillip (1980) The First New Zealanders. Hodder and Stroughton, Auckland.

Howe, K. R. (1984) Where the Waves Fall. George Allen and Unwin, Australia.

Howe, K. R. (2003) The Quest for Origins. Penguin, New Zealand

Jobling et al (2004) Human Evolutionary Genetics. (UK/US) Garland Science, New York.

Lewin, Roger (1999) Patterns in Evolution. Scientific American Library, New York.

Olson, Steve (2002) Mapping Human History. Houghton Mifflin Company, New York.

Putman, Rory (1988) The Natural History of Deer. Cornell University Press, New York. (UK/US)

Ridley, Matt (2000) Genome. Harper Collins, New York.

Swartz, Marc J. and Jordan, David K. (1980) Culture - The Anthropological Perspective. John Wiley and Sons, Canada.

Underhill et al (2001) Y-Chromosome Haplotypes and Implications for Human History in the Pacific. Human Mutation 17: 271-280.