Most of us have no trouble with the “Theory of Gravity” except for a few members of the flat earth society.
Most of us have no trouble with the “Theory of Relativity”, although many don’t understand it.
Most of us have trouble with the “Theory of Evolution” because we cannot fit the evidence to our pre-existing assumptions, preconceptions and prejudices, our Chinese drover’s clever dog syndrome (“Conception” [The Chinese Drover’s Very Clever Dog]).
For example I was well into assembling this evidence before it was pointed out to me some members of the prosecution will maintain the earth is only about ten thousand years old. The science of geology is just one piece of evidence that shows the earth is very much older than just this. We’ll look at another piece soon [The Horse].
Geology, like all knowledge, has developed gradually through the interaction of conflicting or opposite interpretations of the available evidence (Gohau 1991). Ideas or theories have been put forward by individuals, and elements of the theories that seem to be correct have eventually become generally accepted.
Of course at any particular time “a basically incorrect hypothesis may perform a useful function” (Fyrth and Goldsmith 1965). But if a theory can solve problems previously not even understood to be related, or if it can be used for predictions and other practical applications, it is usually accepted as being true. After all the theory of gravity is only a theory. It is generally accepted as being true because it explains so many different phenomena, makes predictions and can be used for practical purposes. We don’t actually know how gravity works. This is probably just as well, or governments would find some way to tax it, or some private company would claim ownership. Imagine having your gravity cut off because you’d forgotten to pay your bill.
Geology’s progress was held up until about 200 years ago because it is a problem for us humans to accept incomprehensibly long time scales. But geology (like most things) got serious when economics came into it.
The invention of the steam engine and factory methods of production, especially in the spinning and weaving industries, gave rise about 1800 AD to the Industrial Revolution (Fyrth and Goldsmith 1965). The economic and free trade ideas of such people as Adam Smith, along with ideas of freedom resulting from the American and French revolutions also played a huge part in its development. Of course like anything new in society the Industrial Revolution led to disruptions and change. It had first got seriously under way in England, but its spread to mainland Europe led by 1848 to uprisings against the governments of Belgium, France, Italy, Germany, Spain, Portugal and Switzerland (Fyrth and Goldsmith 1965).
The Industrial Revolution required large amounts of coal, and the construction of canals to transport it. Humans could now clearly see what was beneath their feet.
James Hutton, a Scot, is an important figure in geology’s development. Originally he had studied blood circulation in the human body. He later turned to farming. Therefore he knew plants need soil to grow in, and soil is formed from the weathering, erosion and transport of material from higher land. He also knew that a great deal of soil is continually washed out to sea and lost. It was already widely accepted that compacting of material under the sea had formed most rocks, but it was believed a series of huge and rapid convulsions of the earth, such as Noah’s flood, had lifted them up.
With his idea of circulation, Hutton wondered if the Earth was a bit like the human body, and eroded material was continually recycled. When he actually looked at the evidence by examining rock layers he realised it was completely possible there had been a whole series of cycles of erosion and uplift rather than just a few sudden ones.
When rocks are formed under water they are laid down in horizontal layers, or strata, the uplifted remains of which members of the jury have probably seen in many places around the country. As they are lifted up, these strata are often tilted. Hutton found several places where these hardened, uplifted, tilted strata had been eroded and subsequently overlaid with a different type of rock with strata tilted in a different direction, or even still horizontal.
Hutton came to realise the rocks were much more ancient than people at the time believed (Jones 2000). In fact he wrote, “we can find no vestige of a beginning, no prospect of an end” (Tudge 1996). Hutton also introduced the idea that “The present is the key to the past” (Winchester 2002), although other geologists had already used the same idea to some extent (Gohau 1991).
In 1785, Hutton presented his ideas, including his idea that heat from the Earth’s core was involved in the formation of rocks, to the Royal Society of Edinburgh. His paper was published for a wider audience in 1788 and immediately attracted a huge amount of opposition, mostly on the grounds it contradicted the biblical account (Baxter 2003). But as more evidence in their favour accumulated, geologists in Britain gradually accepted his ideas in the years after his death (in 1797). Hutton didn’t solve all of geology’s puzzles. For example his theory of what causes the uplift that forms mountains was not quite correct. This side of geology had to wait until the 1960s.
Meanwhile, the next big breakthrough in the early days had been in 1799 when William Smith pointed out that “the same strata are always found in the same order of superposition, and they always contain the same peculiar fossils” (Winchester 2002). He realised he could use these different fossils as markers to place any local sequence into a much wider and deeper sequence. He published a geology map of England and Wales in 1815 (Baxter 2003). The science of geology then took off.
In his book “Principles of Geology”, produced in about 1830, Sir Charles Lyell (born the year James Hutton died) combined all these ideas and introduced the theory that came to be called “uniformitarianism”. This states that geological processes are largely the same today as they have always been. The theory has served geologists well in their search for minerals and oil since those early days and so it is probably basically correct. But Lyell also obviously had problems with mountains.
Charles Darwin was given a copy of Lyell’s book to read during his long voyage on the Beagle (Baxter 2003).
Several pieces of evidence including precise survey methods have established that the continents are slowly moving round the earth’s surface. The sea floor expands from mid-ocean ridges and pushes under the land at what are called subduction zones. As material from the sea floor is pushed down it raises a chain of mountains and causes earthquakes and volcanoes along the subduction zone. As the Himalayas show, the mountain chain can actually be a long way inland.
The rate of movement may have been more rapid in the past, but nobody has provided any evidence for this and it seems unlikely. In fact when the continents are fitted back into their presumed original position mountain ranges that appear to have been pushed up by even more ancient continental movements are revealed as being continuous across different continents. The best example is the line up of the Appalachian Mountains of North America with the Highlands of Scotland and the Scandinavian peninsular. This shows that the Atlantic Ocean opened after the mountains had been formed. Continental movement has been going on for much longer than just any relatively recent movement.
The theory of continental drift (pdf), first seriously proposed by Alfred Wegener in 1912 (Gohau 1991) and proved in the mid 1960s, was able to explain so many things that had previously been impossible to understand (Tudge 1996). As the defence said earlier we consider any new theory to be true when it can provide consistent solutions to many different problems. Continental drift explained away the many ancient similarities between plants and animals on what are today widely separated landmasses. No longer was it necessary to imagine ancient land bridges where no evidence for them could be found. The problem of mountains was also solved.
The evidence indicates that material has been continually eroded off the land, deposited on continental shelves or in deep ocean basins and has been pushed up and recycled by the same processes as are operating today (Stevens 1985). There have been huge landslides on a fairly local scale of course, but this doesn’t negate the basic idea of uniformitarianism.
But the flat-earthers do have a point, because for most practical purposes the earth can be thought of as being flat. For example the volumes of both water and continental crust are roughly constant although global temperature does alter the volume of seawater, and the amount of evaporation from it. Apart from around freezing point, water behaves like most things and expands as it warms and contracts as it cools. Evaporation from the sea falls as rain or snow. Rain fairly rapidly runs off the land, carrying material down to the sea, but on high mountains or near the Poles, snow accumulates as ice in glaciers and the frozen water cannot return to the sea for some time. Changes in sea volume and the shape of the seafloor affects sea level. Change in sea level alters the area of land by exposing the regions of continental shelf.
The process can be shown diagrammatically.
But some members of the prosecution still claim that the present geology of the earth is the result of a relatively recent single gigantic flood. They say that the distribution of mountains, rock types and fossils demonstrates a succession of plant and animal types washed into hollows by this single flood. However, when examined, this explanation of the evidence contains so many internal contradictions, and selectively ignores such a huge amount of relevant evidence, that only someone with no real conception of geology could find it adequate. It would, in any case, be a very blatant case of juggling the evidence to fit a mythconception, Chinese drover’s clever dog syndrome.
I suppose it is remotely possible a whole series of gigantic floods could explain the evidence and, as I said earlier, this was exactly what geologists believed until after James Hutton’s time. Very few believe it today. The names of the most recent geological periods, “Tertiary” and “Quaternary”, remain from the earlier idea, although these names may be slowly dropping out of use. “Primary” and “Secondary” were dropped long ago. Primary mountains were believed to be the original ones God had created in the beginning.
There is also other evidence demonstrating overwhelmingly that the Earth is very much older than just the ten thousand years seriously claimed by some members of the prosecution. Many of them even claim that all creatures survived an even more recent devastating flood. Unfortunately for these claims, the fossil record shows that a whole series of continental movements and changes in sea level have been important in many species’ evolution. Surely it is impossible to believe this evolution has all happened within just the last 10,000 years, or less.
For example the evidence shows that, while being a drawn out process, the evolution of the horse (Equus caballus) was relatively straightforward. However, evolution-deniers often claim that the fact its evolution is no longer seen as being quite as straightforward as it was once thought to be, is proof of their own beliefs. The logic of their argument escapes me. The book published by the Watchtower Bible and Tract Society “Life – How Did it Get Here” remarks concerning the horse’s evolution “the fossil species of Eohippus show little evidence of evolutionary modifications.” Well no. It may only be a matter of a name but once it becomes slightly modified it is confined to more recent layers of rock and is no longer classified in the genus Eohippus (or, more correctly, Hyracotherium). It becomes Orohippus.
Before we go any further it might pay to have a quick look at the double names by which scientists identify species and classify them into a hierarchy of groups.
The first name is the “genus” and is like a surname or family name. It is the first step upwards in the classification of types, or species, into groups called “family”, “order”, and so on. We won’t go any further in that direction for now. But horses, donkeys and zebras are obviously more similar to each other than any of them are like any other species. They are all grouped into the genus Equus.
The second name is the actual “species”. Each species has a description of what is called a “type specimen”, an individual that defines the characteristics of all the animals, for example, included within that name. This is usually the first individual described under that name.
There are six living species in the genus Equus. Just two of them live outside Africa: the horse (Equus caballus), originally from north of about 45° N in Europe and Asia, and the onager or Asian ass (Equus hemionus) from south of 45°. The African donkey (Equus asinus) from northeast Africa and three species of zebra found in the rest of Africa: Grevy’s (Equus grevyi), the mountain zebra (Equus zebra) and the plains zebra (Equus burchelli) make up the four African species.
Almost all of these species are also divided into regional varieties called “subspecies”. Subspecies are usually defined as being able to form fertile hybrids. They are given a third name. For example both Equus burchelli boehmi (Grant’s zebra) and Equus burchelli chapmani (Chapman’s zebra) (link) are subspecies of the plains zebra. But the jury will see next (“Species” [Labels]) that the distinction between species and subspecies is difficult to define. For example the Tibetan ass and the Mongolian wild horse are each sometimes regarded as being a further two separate species rather than being just subspecies of Equus hemionus and Equus caballus respectively. In the case of Equus caballus this is justified by the fact that the Mongolian horse and domestic horse have a different number of chromosomes, but on the other hand they form fertile offspring (“Hybrid Vigour and Inbreeding” [Hybrid Vigour]).
All the single names in Italics that follow are genus names, and they usually cover several species.
The defence will go into how “Evolution” actually works after we’ve looked next at “Species” in more detail. But at the beginning of the Eocene geological epoch (55 million years ago) the genus Hyracotherium was present throughout both Europe and North America, but not anywhere else (a few fossils have been found in the Far East). This odd distribution was because the Atlantic Ocean had not yet completely separated North America from Europe, and a shallow sea also separated European animals from Asian ones (Flannery 2001). Only in North America did Hyracotherium later develop towards the horse. In Europe it remained largely unchanged and at one time was thought to have developed into the modern hyrax or cony of Africa and the Middle East (Tudge 1996). Hyracotherium was about the size of a small dog and had four toes on its front feet and three on its back feet.
Most scientists believe Hyracotherium itself had evolved from an even earlier kind of mammal called Condylarthra. By about sixty million years ago Condylarthra had diversified into a huge variety of genera and species, all with five toes on each foot. Some types were carnivorous with fangs and claws (Flannery 2001). Animals like rhinos, tapirs and possibly even elephants might all come from branches of this original kind, but the carnivorous ones eventually died out (Kurten 1971). If some controversial mitochondrial DNA evidence proves to be correct (Lewin 1999) all hoofed animals, and even whales (Jones 2000), may have come from the Condylarthra kind. The same evidence would put elephants on a more distantly related line. So we don’t know the exact details before Hyracotherium, but we shouldn’t throw the baby out with the bath water.
The pattern revealed in the fossil record shows that in North America the shape of Hyracotherium’s teeth changed with the passage of time and generations. As the animals change, the names they are given change. For example the first modification is called Orohippus. Lines also diversify through time, and species migrate around North America, most fairly rapidly becoming extinct. Each ancient genus is represented by several species and so there is diversification all the way. But by the late Eocene epoch (37 million years ago) the group had been reduced to just one remaining species and the genus name is changed to Epihippus (Flannery 2001). The process of diversification, change and extinction started again and by the time of the Oligocene geological epoch (30 million years ago) the number of toes on each foot had been reduced to three and the teeth were beginning to look like those of modern horses.
Three-toed horses of the Hipparion genus were able to migrate out of North America at the end of the Miocene epoch, about 5-7 million years ago, via a land bridge between Siberia and Alaska. The latest series of ice ages was yet to start and although other primitive horses had made it out before this time they had become extinct. Hipparion expanded right around Europe and Asia and even as far as Africa, where they survived long enough for early humans to have them for dinner; and I don’t mean as guests. Several types of one-toed horses had already appeared in North America by the time Hipparion was able to get out. Modern horses (Equus) didn’t begin to make it into Asia until the early Pleistocene epoch, 2-3 million years ago though. The true horse (Equus caballus) didn’t make it out of North America until less than a million years ago (Jones 2001).
This means horses, zebras, asses and donkeys have probably separated only in the last 2-3 million years. They can still interbreed but the offspring are usually sterile. Although the development of isolating mechanisms and incompatible genes can mean the differences between species are not simply a function of time it seems that, at least for this group of species, 2-3 million years has not been a long enough separation to prevent the production of offspring. Modern elephants (African, Indian and mammoths) started their diversification a little more than 3 million years ago and the surviving species don’t form hybrids. You will later see that Homo erectus, the “First Humans”, evolved more recently than 2-3 million years ago and so, in the absence of other evidence, there is no reason to expect various groups descended from this species could not have successfully formed hybrids.
Incidentally, horses actually died out in America soon after the arrival of the ancestors of the American Indians. The wild horses there now are descended from domestic ones brought in by Europeans in the last 500 years.
Genetic evidence shows humans originally domesticated the horse in several different regions, and it was a prolonged and gradual process covering several thousand years (Jones 2001). The first step was probably the herding of horses for meat. Herding of different semi-wild animals had developed over quite a wide region of Europe and Asia by the end of the ice age, around 10,000 years ago (Clark 1969). For example reindeer were herded in Western Europe, and goats and gazelles in the Middle East. The same process probably achieved domestication of sheep and cattle, and reindeer are still herded under a similar system in the Arctic regions of Europe and Asia. The main centre of horse domestication seems to have been the Central Asian steppes. As the jury saw earlier its domestication was probably associated with the original expansion of the “Indo-Europeans” [The Chariot].
The first horses domesticated on the steppes were the size of a small pony (1.2 to 1.3 metres), the same height as the wild horses still found in Mongolia. Today’s thoroughbred horses and many draught breeds are much taller, over 1.6 metres. So the horse has continued evolving since it was domesticated, and is probably the product of hybrids between several different varieties or subspecies (Jobling et al 2004).
See next :: 'Species'
Baxter, Stephen (2003) Revolutions in the Earth. Weidenfeld and Nicolson, London.
Clark, Grahame (1969) World Prehistory. Cambridge University Press, UK.
Flannery, Tim (2001) The Eternal Frontier. Text Publishing, Australia.
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.
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.
Kurten, Bjorn (1971) The Age of Mammals. Weidenfied and Nicholson, London.
Lewin, Roger (1999) Patterns in Evolution. Scientific American Library, New York.
Stevens, Graeme (1985) Lands in Collision. Science Information Publishing Centre,
Tudge, Colin (1996) The Time Before History. Scribner, New York.
Winchester, Simon (2002) The Map that Changed the World. Penguin Books, UK.