Human Evolution on Trial - Pacific Population

'Pacific Population'

As you move further into the Pacific Ocean to the north, south or east of the Solomons the islands become progressively more isolated. Islands beyond the Northern Solomons remained uninhabited by humans until the Austronesian-speaking people arrived. The islands’ progressive isolation has also had consequences for Pacific bird populations.

Various species of birds have periodically expanded from Asia through New Guinea to the Bismarks, then progressively to the Solomons, to Vanuatu, New Caledonia, Fiji and Samoa (Mayr and Diamond 2001). There are fewer species the further east you go as the islands become progressively more isolated. A much smaller movement back the other way of species that have developed in the islands of the Pacific Ocean has also occurred.

Several widespread kinds of bird, especially rails (classified into the Order Gruiformes), ducks (Order Anseriformes), pigeons (Columbiformes) and small birds (Passeriformes) became flightless once they had reached the various islands. Consequently there was a loss of gene flow between the islands. As a result on each separate island the flightless members of these groups have, or more usually had, become different enough to be classified as separate species. Their extinction coincides with human arrival.

In fact the jury will see that human expansion through the Pacific followed much the same pattern as did bird expansion even though until recently they couldn’t fly. Of course sailing and flying are similar in that they are each influenced by the wind.

The Canoe

Many writers on the subject of the Austronesian migration have trouble understanding the reason for their rapid expansion. It seems the writers assume the islands are the same today as they have always been. McGlone et al (in Sutton 1994) call finding previously unoccupied islands the prehistoric equivalent of winning a lottery. There would have been huge populations of birds and animals with no fear of humans and undisturbed fish and shellfish in the surrounding sea. Any islands already occupied would have been quickly bypassed in the search for more of these paradises. Gene flow would be preceded by the line, “Come with me, love. I’ve just found another uninhabited tropical island”.

Technological developments such as the dugout canoe, outriggers and possibly sails of a primitive sort, enabled Austronesian-speaking people to be the first humans to occupy the Southern Solomon Islands. They eventually reached Vanuatu and islands as far away as New Caledonia (and possibly Norfolk) and ultimately, by 1000 BC, Samoa and Tonga via Fiji (Howe 1984). People also moved into the Marianas about this time.

Any idea this involved a single migration is completely wrong though. As a general rule, a migration route once opened is used regularly. It was probably the innovation of the double-hulled or single outrigger canoe that allowed the later phases of this expansion to and beyond eastern Melanesia (Howe 2003) but it seems to have been another thousand years before humans were able to expand further east beyond Tonga and Samoa. That required a further technological development and my guess is it involved an improvement in sailing technology. We will come back to this later in [The Sail].

The jury saw in “Change” [Galapagos Finches] that during times of plenty the boundaries can become porous. You have also seen (“Polynesian Origins” [Genes]) that the Y-chromosome and mtDNA evidence does show that as the Austronesian-speaking people moved from Taiwan into the Pacific Ocean they mixed and bred with people they met on the way and picked up elements of their culture. A great deal of gene flow occurred.

Who were these people that the Austronesian-speakers mixed and bred with as they made their way south out of Taiwan 5000 to 6000 years ago?

On many smaller islands, probably no one. Many islands immediately south of Taiwan had probably also become uninhabited and were paradises for these first Austronesian-speaking people. Even at the height of the last ice age while much of Island Southeast Asia had been connected to the Asian mainland most of the Philippines, Sulawesi and eastern Indonesia remained separated as islands. Palawan, in the Philippines, was connected at times to Borneo but not connected to the Philippines proper. The defence will later suggest though that about 50,000 years ago the very first immigrants “Into Australia” [Wallace’s Line] may have come by this route, probably on primitive bark or bamboo rafts.

The rise in sea level at the end of the ice age led to a decrease in the size of islands. This increased the isolation of any earlier human populations and led to inbreeding and the depletion and even extinction of populations on many islands. Some anthropologists claim elements of earlier populations did survive in parts of the Philippines and Sulawesi, but these supposed earlier groups now speak Austronesian languages (Bellwood 1978). Of course residents may have adopted the incoming languages. Other anthropologists think the people are more probably remnants of the first wave of the movement from Taiwan.

But in other parts of Southeast Asia and especially in New Guinea, the Northern Solomon Islands and Australia the movement from Taiwan definitely encountered people who had been there a very long time.

Hoabinhian

In New Guinea erosion interpreted as resulting from clearance of slopes is dated to 10,000 years ago (quoted in Jennings ed. 1979). Pigs may have been introduced to New Guinea as early as this and agriculture there may have begun this early too. Ancient edge-ground stone axes found in New Guinea are also dated at more than 10,000 years ago (Howe 1984). Similar sorts of axes are found from about the same time in the “Hoabinhian” culture of Southeast Asia.

The Hoabinhian began long before 10,000 BC and was spread through South China, Vietnam, Thailand, Malaysia, Sumatra and Borneo (map 5). The Hoabinhian people were early farmers. They were the same physical type as modern Melanesians and Papuans (Clark 1969) and people of similar physical type were found as far afield as India, the Northern Solomon Islands and possibly even Australia. Hoabinhian people may have spoken languages unrelated to Austronesian, Austric or even the whole Sino-Tibetan group. I will explain in “Into Australia” [Explanation] why it is my bet they spoke languages that were part of the sort of catchall group, the “Indo-Pacific Family”. As I said in “Polynesian Origins” [Language Families] Indo-Pacific languages survive in the Andaman Islands, in Melanesia and in parts of New Guinea.

This evidence of inter-island connections long before the Austronesian-speaking people had arrived implies there was already some level of boating technology although not sophisticated enough for people to reach the Southern Solomon Islands. Travel over very large distances of open sea is not necessary to account for contact within the Hoabinhian region. The culture had spread before sea level rose at the end of the ice age, about 10,000 years ago.

Map 5 shows the Hoabinhian’s distribution. Its distribution corresponds reasonably strongly with a genetic extreme that shows up in Cavalli-Sforza’s (1994) maps of both the second principal component for Asia and the sixth principal component for the world. In both maps the genetic combination weakens gradually away to the northwest in exactly the same way as the European genes in map 2 did (except they weakened towards the southeast). The opposite genetic extreme in the Asian map occurs across the far north. The bold dashed line in map 5 shows the boundary between the two Asian genetic extremes.

Although map 5 shows an expansion and gene flow from Southeast Asia at some time agriculture in the Middle East does look to be independent of the development of agriculture in that region. The crops domesticated are different. In the Middle East food crops are mostly grains and pulses (lentils and peas). In Southeast Asia the crops are sugar cane, taro, breadfruit, coconut and bananas although rice was later domesticated in South China or Southeast Asia and has become a major food source. Agriculture also developed independently in America. There the crops included maize, pumpkins, tomatoes, potatoes and sweet potatoes or kumara. In Africa sorghum, millet and yams were domesticated (Stringer and McKie 1996). In “Out of Africa” [Asia] the defence will elaborate on evidence for an ancient genetic expansion from New Guinea that reaches all these regions though.

The first agriculture probably developed when people realised that by weeding natural stands of food-plants production increased. But the defence will point out later, in “Evolution” [The Human Influence], that the development of farming was an extremely gradual process. Although throughout this story I will suggest that any particular change in technology or culture has been invented only once and then spread as far as circumstances allowed I believe the evidence shows agriculture developed independently several times. There is the possibility the idea of weeding natural stands of food plants occurred only once and very early in our history though. This very basic farming would leave no trace for us to find today.

Agriculture didn’t make it to Australia even though the edge-ground axe did make it to the north of that continent (the axes shown in map 5 are actually Australian). Either agriculture was lost because Australia was unsuitable or, more likely, the axe and agriculture were separate developments. In fact the edge-ground axe actually got to Australia much earlier than 10,000 years ago. Skeletal material possibly dating to about the time of the introduction of this type of axe to Australia indicate it may have been brought in by the movement of a particular kind of people from Southern Indonesia. The defence will follow this up in “Into Australia” [Kow Swamp].

Polished stone tools and new pottery styles, probably associated with the Austric-speaking people, replaced the Hoabinhian culture in Malaysia and Thailand about 3500-3000 BC. Both pottery and the polished stone axe with quadrangular cross section appeared in Borneo by 2500 BC (Bellwood 1978).

Mixing

The Austric-speaking people who had moved south from around Taiwan some time before 3000 BC didn’t necessarily look like modern Taiwanese. The modern population of Taiwan is mostly descended from a more recent expansion southward starting about 2000 BC with the Lung-shan rice-growing people from the Hwang Ho River valley in northern China (Clark 1969). It is possible an earlier movement of these people may have contributed to any population that had moved from the mainland to Taiwan. But the population that had developed in Southern China and Taiwan by 3000 to 4000 BC was basically a hybrid between the indigenous Southeast Asian Hoabinhian people and the incoming microlithic-using people from the north (probably from around the Sea of Japan, see “Polynesian Origins” [Japan]). The defence suggests that the boating improvement that led to the expansion was in fact a hybrid of northern and southern technology. Again I would point out that new technology leads to times of plenty and at such times the boundaries become porous.

Migration of the resulting mixture of people into Southeast Asia was both overland and by sea. The original, or proto, Austric language these people spoke split into several groups (“proto” means “first” or “earliest form of” as in prototype). Movements by land introduced the Thai-Kadai and Austroasiatic languages to Southeast Asia (languages of Thailand, Vietnam, Laos and Cambodia, see “Polynesian Origins” [Language Families]) and by sea the Austronesian language group.

So the people who moved into the perhaps temporarily vacant Island Southeast Asian sub-point of the human star became a hybrid of two kinds of people. These were the Melanesian or Australian Aboriginal-looking people who, at the time, lived as far north as South China and the people from North China or Japan who brought technologies introduced there at the end of the ice age. A mix of people from the Australian and East Asian points of the human star (map 1). In other words there was not simply total replacement of one population by another. The present Island Southeast Asian population lies in a hybrid zone between two other different populations (“Hybrid Vigour and Inbreeding” [Wave Theory of Evolution]).

The fact the dingo arrived in Australia from Southeast Asia some time between 6000 and 3500 years ago (Bellwood 1978) shows the boating people probably reached the mainland of Australia as well but any genetic contribution was apparently minimal. The people already there greatly outnumbered any immigrants although a more modern stone technology seems to have been introduced about then (the Pirri points). People in the two main points look very different from each other though. They had obviously been living in each region long before any movement out from Taiwan started.

The maps of the first principal component (therefore accounting for most of the genetic variation) for both just Asia and for the whole world support this interpretation. One genetic extreme in the Asian map is fairly much a combination of maps 4 and 5 already presented as evidence. The defence sees no need to use this Asian map as further evidence. A boundary between genetic extremes that shows up in the world map is fairly similar. The jury will see the world map in “Into Australia” (map 16).

The defence has already suggested the population around the Sea of Japan was itself a hybrid between the microlithic-using people and the original inhabitants (“Polynesian Origins” [Japan]). In Parts IV and V the jury will see that the populations in all points of the human star are the products of a complex mixture of various human migrations. But before we can easily follow the pattern of these migrations back to and beyond the origin of our species the defence needs to present yet more evidence. We can still learn a great deal about the defendant by examining evidence from more recent times.

Map 6 sums up what we have covered so far. Remember, though, the people on this migration around the Pacific mixed with the local people they met on the way and some locals joined them. The expanding population wave maintained hybrid vigour.

In New Guinea Austronesian languages are spoken in the extreme west, along the north coast and in southeastern parts (Howe 1984) and there is evidence to support a genetic contribution from the Polynesian’s ancestors in these areas. People from the region also seem to have contributed genes, including Y-chromosome, to the Polynesian wave of expansion.

The defence will later use the Polynesians’ expansion into an uninhabited region of the earth to explain several ancient examples of human migration. It also provides us with a good example of a narrowing gene pool. We will first need to come back to its origin.

Lapita

Fiji is regarded as being transitional between Polynesia and Melanesia. Some linguists consider the Fijian languages to be the closest to ancestral, or proto, Polynesian (Jennings 1979). In other words the Austronesian dialect carried east from those islands became the original Polynesian language.

The first people to reach the Fiji / Tonga / Samoa area (Western Polynesia) are associated with a pottery style called Lapita (Howe 1984). These Lapita-using people had moved from west to east (Jennings 1979), the pottery type first appearing in the New Britain / New Ireland area about 2000 BC (indicated by the asterisk in map 6). It is ultimately descended from pottery styles further west in Island Southeast Asia. The pottery spread first across Melanesia, where it is intrusive on earlier pottery cultures. We will come back to pottery much later during this story (“The Last Point”) but it is interesting the oldest pottery in the world has been found in Japan (for example see Klein 1989). To remind the jury of this I have included the Jomon pot from map 4 at the top left in map 6.

The Lapita economy was primarily fishing based but bones of sea mammals, turtles and birds show these were also eaten. All the newly discovered islands had huge populations of nesting sea birds, turtles and seals along with flightless rails, ducks and megapodes (Australian brush turkeys). Fish and shellfish would also have been much larger than their descendants are (McGlone et al in Sutton 1994).

There is a great deal of evidence for to and fro travelling during Lapita times. Various pottery styles and rock suitable for tools were exchanged over long distances. Lapita people therefore had simply introduced a yet more sophisticated boating technology into the region and then developed more complex trading networks.

As well as pottery the Lapita people carried on the tradition of large stone adzes they had inherited from their ancestors in Southeast Asia. They also took pigs, dogs, poultry and the available cultivated plants with them.

The greatest distance between any two island groups within the Lapita-ware area is between Fiji and Vanuatu. As a result people in the islands of Fiji, Tonga and Samoa at the eastern margin eventually became isolated from the rest of the Lapita complex. Fishhooks associated with the Lapita pottery using people in Tonga and Samoa are very similar to those found in the eastern Solomon Islands dated at both sites to about 800 BC (Jennings 1979) and so Lapita contact was kept up at least until about that time.

The Melanesian look of many Fijians is assumed to be the result of a more recent push eastward of Melanesian physical types i.e. populations in Melanesia adopted and perhaps improved the technology that had virtually passed them by, and then they followed on (Howe 1984). There is evidence the next migrations, to “Eastern Polynesia” [Marginal Polynesia] and then to New Zealand, were products of the same phenomenon. Even the first human migration “Into Australia” [Explanation] seems to have involved a similar process to the whole Austronesian expansion.

But at that remote time Java and Flores rather than the Northern Solomon Islands were the most distant, previously occupied land. Perhaps we could assume that most human migrations have been similar. They occur as waves and often collect up other groups of people as they pass by. They are very seldom a single movement by a single group of people. Certainly the migration of Europeans around the world over the last few hundred years fits the pattern.

Several waves of immigrants certainly seem to have arrived in Fiji. A new style of pottery was introduced by 100 BC. This style is called the Navatu culture. It has connections to the west from about 1200 BC, via New Caledonia, as far as Southeast Asia. There is a further change in pottery styles in Fiji about 1200 AD and the beginning of fortifications (Jennings 1979). This later pottery style probably has its origin in central Vanuatu. Although many people divide the Fijian languages into eastern and western groups people associated with these two pottery incursions are assumed not to have altered the language. The incursions did alter the genetic make up of the Fijian people though, and this shows again that once a migration route is opened up it is used regularly. There are a continued series of pulses along it. The jury will see that, as for Pacific bird populations, this whole process has happened again and again, long before our species even evolved.

Pottery ultimately died out in Polynesia. This loss must have been associated with some alternative method of carrying water in canoes. Gourds or coconuts are an obvious alternative but I’m not aware of any study on gourds in the Pacific. On the other hand the loss of pottery may have been due to a lack of suitable clay at some stage in the movement.

I understand it is impossible to say whether Samoa or Tonga was settled first after Fiji. Both groups of islands 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”, “Tahiti” (tawhiti) means “distant”, “Tuamotu” may mean “islands beyond” and “Tongareva” (rewa) may mean “float south”. The defence suggests these names of islands and island groups are significant for the study of Eastern Polynesia’s settlement.

The Sail

What enabled humans to make their sudden burst through Eastern Polynesia? Colonisation was against the prevailing wind, in the tropical Pacific wind blows almost continuously from east to west. But the Equatorial Counter Current flows from west to east, and during El Niño years the easterly winds are not as intense. Drifting on the equatorial current and sailing back with the wind would have allowed rapid exploration but does imply a more equatorial navigation route than is usually considered. However we know Polynesians had crossed the equator to reach Hawai‘i by about 400 AD. The route to Hawai‘i was presumably along islands on the Christmas Island Ridge.

The first stages of the human migration into Eastern Polynesia took place between about 300 BC and 300 AD, and I would suggest it resulted from an improved sail. It’s actually possible the sail was invented independently in several parts of the world (Howe 2003). But the sail as developed by Greeks and Phoenicians, in the Mediterranean Islands subpoint of the human star (“The Last Point” [The Sea People]), may not have been introduced to the Indian Ocean until about 325 BC. In that year Alexander the Great organised an expedition down the Indus River and back west along the coast to the Persian Gulf. Before then, about 500 BC, the Persian King Darius Hystaspis may have sent the Greek, Scylax, to explore the Indus River and Arabian coast, but the later trip by Nearchus under Alexander is well documented. The people encountered on the coast of Baluchistan during this voyage evidently had a primitive technology and so there had almost certainly been very little contact between the Indus and Mesopotamian river valley civilisations along the coast before this time (Cary and Warmington 1963).

By the beginning of the second century AD sailors were using monsoon winds in the Indian Ocean to travel between the east coast of Africa and what is today Indonesia. The languages spoken in Madagascar are, like Polynesian, part of the Austronesian group and extinctions on the island indicate humans arrived there at about the same time as they beganm moving eastward into the Pacific beyond Samoa. This is not to say the same population was involved. Technology travels faster than genes and it is almost certainly significant that many Eastern Micronesian islands were also being colonised by 200-300 BC. That the people of the Pacific, with their proven boating ability, would take up and perhaps modify a sail is hardly surprising. The arrival of a new pottery style in Fiji about 100 BC may indicate the technology was carried by a small population movement from further west. Someone called Kiwa may have introduced the advanced sail to Polynesia as, in New Zealand at least, the Pacific Ocean is called “Te Moana Nui a Kiwa” (Kiwa’s Ocean).

Incidentally Bryan Sykes and Matt Hurles (Jones 2001) found that the Y-chromosome of 30% of the Polynesian men they studied descended from Europeans, presumably from sailors, sealers, whalers and missionaries. Peter Underhill et al (2001) found that 15% of the mtDNA of Maori in their study was from European lines and so we’ll now turn to this side of the New Zealand family mix, and their evolution. This will provide the jury with yet more evidence in favour of the wave theory of genetic, cultural and technological evolution.



See next :: Human Evolution On Trial :: 'Indo-Europeans'

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.

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

Gray, R.D. (2009) Language Phylogenies Reveal Expansion Pulses and Pauses in Pacific Settlement. DOI: 10.1126/science.1166858 (see also: Dieneke's Blog)

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.

Klein, Richard G. (1989) The Human Career. University of Chicago Press, Chicago.

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

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

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