The Great Divide

by Peter Watson

  The date is important because no archaeological sites earlier than 20,000 years ago have ever been found anywhere in Siberia. However, there is both genetic and linguistic evidence for an earlier entry into the New World. This evidence is controversial and is not universally accepted. The location of the sites is important because agriculture has never been successfully practised this far north and so early man could not have entered the New World knowing anything of agriculture. This is in itself not surprising for agriculture did not emerge anywhere on earth until about 10,000 years ago but at least that means this is one area where the picture is clear: the Old World and the New both lacked agriculture when the Great Divide took place (though they had dogs).

  The DNA evidence shows that the Chukchi are genetically distinctive. According to the Genographic Project (see below), they have a marker, a distinctive pattern of genes, technically known as M242, and other characteristics, which show that they originated in a single man living about 20,000 years ago in southern Siberia or Central Asia. These markers are also shared with Native Americans as far south as Tierra del Fuego and therefore confirm – for geneticists – that early man entered the New World from Siberia some time after 20,000 years ago.3

  This picture was supported – and amplified – when the first results came in from the Genographic Project, set up in 2005, sponsored by National Geographic but making use of IBM’s massive computational skills. This very large study examined the DNA of around 150,000 individuals on five continents, to draw up the most thorough picture of our genetic history ever mounted. The most basic technique of the Genographic Project was to examine what are termed haplogroups, distinctive and characteristic patterns of genetic mutation, which comprise ‘markers’ on mtDNA or Y-chromosomes and which show how people are related and were related in the past (M242 is a haplogroup).

  This research shows two things that concern us. First, that today’s Native American peoples are very similar to one another genetically and that most of the distinctive markers are somewhere between 20,000 and 10,000 years old, clustering around the 16,000–15,000-year mark. The significance of this timing is that it was during what is called the Last Glacial Maximum (LGM), the era – between 20,000 and 14,000 years ago – when the vast glaciers of the last Ice Age reached their greatest extent, when sea levels were 400 feet below where they are now, and when the Bering Strait would have comprised a land bridge between Siberia and Alaska.

  One haplogroup located on the Y-chromosome is found in Native American men living all the way from Alaska to Argentina and, together with another haplogroup descended from it, is almost the only Y-chromosome lineage found in South America.4 In western North America there is another lineage, which appears to have arrived in the New World later and never to have got as far as South America. But between them, these markers account for 99 per cent of Native American Y-chromosomes. On top of that, there are only five mtDNA haplogroups in Native Americans, in marked contrast to the dozens of mtDNA and Y-chromosome lineages found in Eurasia and Africa.5 An important point about the second lineage, the one found in western North America and known as haplogroup M130, is that it is also found in South East Asia and in Australia, suggesting that this second, later migration into the Americas comprised people who travelled up the Pacific rim, the east coast of Asia and entered the New World around 8,000 years ago, when the Bering Strait was again submerged. They therefore must have migrated by boat. This lineage typically appears in Indians speaking Na-Dene languages, the second major linguistic family of North America (see below).

  The third piece of evidence was another large inquiry, published in 2007, by a team of twenty-seven geneticists from nine countries coordinated by Sijia Wang from Harvard.6 This team examined the genetic markers in 422 individuals representing 24 Native American populations in North, Central and South America and compared them with 54 other indigenous populations world-wide. The main results of this study were as follows:

  they found that Native American populations have lower genetic diversity and greater differentiation than populations from other continental regions (overlapping with the findings of the Geno-graphic Project referred to earlier);

  there was decreasing genetic diversity as a function of geographic distance from the Bering Strait and decreasing genetic similarity to Siberians; the groups most similar to Siberians were the Chipewyan population (Na-Dene/Athabaskan) from northern Canada and the least similar were those in eastern South America;

  there was a relative lack of genetic differentiation between Mesoamerican and Andean populations;

  they found a scenario in which coastal routes were easier for migrating peoples to traverse in comparison with inland routes;

  they found some overlap between genetic similarity and linguistic classification;

  the study showed there was a particular allele (genetic variable) ‘private’ to the Americas (i.e., which exists only in the DNA of indigenous Americans), supporting the view that much of New World ancestry ‘may derive from a single wave of migration’.

  This picture is again overall broadly consistent with the evidence from the Genographic Project, and from the analysis of Chukchi DNA, in showing a single entry into the Americas, from Siberia, by a group that is roughly 550 generations old – in other words, who arrived in the New World between, say, (550 × 30 =) 16,500 years ago and (550 × 20 =) 11,000 years ago, probably using a coastal route rather then the inland, inter-glacier route (again, see below). Since the study by Sijia Wang and his team, other surveys, not quite so large, have nonetheless produced fairly similar results regarding the time of entry of ancient peoples into the Americas, but have suggested the entry occurred in two waves not one, the first at ~18,700 years ago, the second at ~16,200 years ago. As will be seen, this fits in with the linguistic evidence presented below.7

  It is only fair to emphasise at this point that there are a handful of DNA studies that suggest a much earlier entry of peoples into the New World – some at 29,500 years ago, some even at 43,000 years ago.8 However, the latest and largest studies – the Genographic Project and that by the Sijia Wang team – not only agree with each other, broadly speaking, but they also agree with the archaeological evidence discovered all across North America, from Alaska to New Mexico. Some of this evidence is outlined immediately below but there is a more extended discussion in chapter three.

  A second kind of biological evidence comes from the work of Christy Turner, at Arizona State University, who is an expert on the evolutionary development of human teeth.9 In particular, Turner has looked at the crowns and roots of 200,000 teeth of prehistoric Americans, Siberians, Africans and Europeans because (a) they show well how populations adapted to different environments, and (b) they are, he says, more stable than other evolutionary traits, and tend not to vary so much between males and females or between old and young. For our purposes, his work is most interesting where it distinguishes between what Turner calls ‘sinodonty’ and ‘sundadonty’. Sinodont teeth, found mainly among northern Chinese and north Asian (Siberian) populations in general, are characterised by ‘incisor shovelling’ (scooped-out shapes on the inside of the tooth), double-shovelling (scooping out on both sides), single-rooted upper first premolars, and three-rooted lower first molars. Turner has found sinodonty in the excavated remains of northern Chinese skeletons that go back at least 20,000 years.

  Sinodonty, he finds, is confined to northern Chinese and northern Asian populations and in ancient Alaskan and other northern American populations. In contrast, such Upper Palaeolithic skeletons as have been found further west – in the Lake Baikal area, for example – do not display sinodonty, nor do teeth from ancient burials in European Russia. The same is true too of ancient remains found among South East Asians. (Turner calls this group ‘sundadonts’ because in Palaeolithic times South East Asia, like Beringia, was above sea level, the continental shelf there being known as the Sunda Shelf, a phenomenon about which we shall have much more to say.) From the spread of sinodonty in
northern Asia and North America, Christy Turner believes that the first Americans developed from people who migrated slowly through eastern Mongolia, the Upper Lena Basin, eastern Siberia, and from there across the Bering Strait into Alaska.

  Still further biological support for this scenario is found in the fact that the infants of some American indigenous tribes are born with the so-called ‘Mongol spot’, a bluish birthmark at the base of the spine that soon disappears and is also found among children in Tibet and Mongolia.10

  Putting all this genetic evidence together, therefore, we may say that the early people from whom virtually all Native Americans alive today are descended, arrived in the Americas – very roughly speaking – about 16,500–15,000 years ago, from somewhere in north-eastern Asia, the area that is now Siberia, just possibly as far south as Mongolia. There may have been small groups of people who found their way to the Americas earlier than that but their effect on later populations was negligible. And there may have been later migrations, the evidence for which will be considered shortly.

  Timothy Flannery makes the point that, although the Aleuts and Inuits in Alaska share many cultural features with north-east Asians (including a form of Eskimo spoken on the Kamchatka Peninsula in Russia, and a variety of acupuncture practised in the Aleutian Islands similar to that used in China), there is very little evidence of people or ideas going back to Asia from the Americas. The only genetic study that throws any light on this is that produced by Nicholas Ray and colleagues who cautiously concluded that some Native Americans crossed back into Asia 390 generations (or 9,750 years) ago. A well-publicised study of the only surviving Yeneseian-speakers, the Kets in central Siberia (several thousand miles from the Bering Strait), showed a linguistic link between the Yeneseian and Na-Dene languages but, genetically, the Kets were very similar to the other Siberian groups around them, and not at all related to the Na-Dene speakers in North America. At the moment there is no satisfactory explanation for this anomaly. But we may conclude, therefore, that the main migration across the Bering Land Bridge went from Siberia to Alaska and occurred – crucially – towards the end of the Ice Age.11

  There is one other piece of genetic evidence we need to consider before moving on. This is the work of Bruce Lahn, at the University of Chicago, who has discovered two genes which are involved in the construction and enlargement of the human brain. Each gene has several alternative forms, or alleles, but in each case one version has become far more common than others among certain populations. This disparity must mean that the effect of this allele was of great evolutionary significance, providing a selective advantage. One of the alleles is a version of a gene known as microcephalin. This first appeared some 37,000 years ago and is carried by 70 per cent of populations in Europe and Asia but is much less common in sub-Saharan populations, where it is carried by between 0 and 25 per cent of people. The second allele is known as ASPM (for Abnormal Spindle-like Microcephaly-associated) and appeared and then spread rapidly in the Middle East and Europe around 6,000 years ago. This allele is absent in sub-Saharan Africa and only weakly represented in East Asia.12

  For these two alleles to have spread so quickly, they must each have conferred some cognitive advantage. For obvious reasons this is material that should be interpreted with the utmost caution, as Bruce Lahn himself has counselled. There is at the moment no evidence these alleles are associated with increased intelligence; set alongside the other results mentioned above, however, these discoveries may have two implications that concern us. First, so far as the mutation that occurred around 37,000 years ago is concerned, one might ask whether this allele had anything to do with the ‘cultural explosion’ that occurred in the palaeontological record beginning around 33,000 years ago, with the notable florescence of cave art in certain areas of Europe. And, by the same token, was the mutation that occurred some 6,000–5,000 years ago in any way related to the development of civilisation that appeared roughly 5,500 years ago? Are we seeing here a link between genes and culture that has not been suspected before, because such results were not available?

  If so, then the second implication may become relevant for the arguments in this book. The first mutation, at around 37,000 years ago, would, if it was so adaptive, presumably have spread quickly throughout Eurasia and included those early people who eventually migrated into the New World. Native Americans should, in other words, have possessed this allele. This is what research shows: microcephalin is virtually universal in New World populations.

  On the other hand, the second mutation, occurring roughly 6,000– 5,000 years ago, would appear to have evolved after early men and women had crossed the Bering Strait, meaning that, in all probability, Native Americans should lack this development. And this too is what research shows: ASPM is completely absent in New World populations.

  It is too soon to say whether microcephalin or ASPM conferred some sort of cognitive advantage on those who possessed it, though its rapid spread suggests that is likely, although simple brain size appears to have remained stable. Nonetheless, this is clearly an area of potentially important genetic difference between Old World and New World peoples. We know from evidence in Iceland, which was inhabited only about a thousand years ago, that substantial genetic differences can arise in such a relatively short time frame, so it is not out of the question that some genetic variation accounts for the differences between the Old World and the New.

  That said, this area of science is still in its infancy, so no more will be made of it here, other than to draw attention to what is a tantalising possibility.

  One final thought on genetics. The relative lack of diversity among Native Americans, compared with the rest of the world, as shown by the Genographic Project and the Sijia Wang team study, may imply one of three scenarios. First, that there was at some stage a genetic ‘bottleneck’ in Beringia, where a small genetically limited group lived for a while, perhaps in a refuge surrounded by the ice, when they were forced to breed within their small community. Second, there was much polygamy later, with some – the more successful – men having several wives and others none (just such a pattern has been observed among the Dani population in Papua New Guinea, for example, where 29 per cent of the men had between two and nine wives, while 38 per cent had none).* Or again, a third possibility, it could be the result of widespread warfare, the burden of which was borne by men, leaving the remainder to father the children (among the Dani, again, 29 per cent of men were observed to be killed by warfare).13

  Among the consequences of such limited genetic diversity would have been the fact that the pace of evolution in the New World would have been slowed in comparison with that in the Old; and it would also have made New World peoples more susceptible to diseases introduced from outside.

  SLEDS AND SEAWEED

  The archaeological evidence for an entry into the New World from Siberia is supported by the great similarity of sites either side of the Bering Strait. A group of locations nearest to the Strait in Siberia was christened (in 1967) by Yuri Mochanov, a Russian archaeologist from the Scientific Research Institute at Yakutsk, as the ‘Dyukhtai culture’, after a site on the Aldan River, which flows north into the Laptev Sea, on the fringes of the Arctic Ocean. Here, mammoth and musk-ox remains were excavated, associated with spear and arrow points flaked on both sides, as well as blades and wedge- and disc-shaped cores – in other words, a distinctive upper Palaeolithic culture, dated to between 14,000 and 12,000 years ago. Other sites, with bifacial tools and blades and even knives, have since been found in the area, together with bone and ivory artefacts. Nothing older than 18,000 years has been unearthed, and the bulk of remains are later. The northern-most site of the Dyukhtai culture is found at Berelekh, near the mouth of the Indigirka River, on the northern shore of Siberia.

  Just as early people appear to have ‘beachcombed’ their way around the south-east coast of Eurasia, to reach China, so they may have beachcombed east from Berelekh along the Arctic Ocean coast of Siberia until they reache
d the Bering Strait – except that it was then land. Some palaeontologists, like Dale Guthrie, emeritus professor at the Institute of Arctic Biology at the University of Alaska, believe that the Dyukhtai microblades were intended to be slotted into antler points as weapons. If so, this could complicate matters, suggesting that this technique, which is also found in North America, was not so much learned or copied by ‘New World’ people from ‘Old World’ people, as a rational adaptation to an environment where reindeer were abundant. In other words, it is not in itself evidence of migration.

  But the fact remains that there are several other cultural similarities between the Dyukhtai complex in Siberia and sites found in Alaska. Both cultures, it should be said, are terrestrial cultures, which do not feature sailing among their skills, suggesting that these early peoples at least crossed Beringia on foot, rather than by canoe or something similar. (One interesting observation that may be more than a sideeffect is that the burial of a domesticated dog was recorded at a site in Ushki, on the Kamchatka Peninsula, dated to 11,000 years ago. Given that, even today, it is easier to move around in the Arctic Circle on foot during winter, with its hard frozen surfaces, than in summer, with its soggy, marshy landscape, this discovery takes on a significance it might otherwise lack.)

  The several prehistoric sites that have been discovered in Alaska show a complicated picture but one that does not necessarily negate the scenario given above. As Brian Fagan says, in his The Great Journey: The Peopling of Ancient America, ‘Despite years of patient endeavour, no one has yet found an archaeological site in Alaska and the Yukon that can be securely dated to earlier than about 15,000 years ago.’14 A caribou tibia was found at the Old Crow site, close to the Alaskan-Canadian border, which had undoubtedly been fashioned by human hands into a ‘fleshing tool’, for removing flesh from hide. To begin with, this and related bones were dated to about 27,000 years ago, but were later revised to only 1,300 years ago. It has also since been discovered that certain other bone ‘tools’ found at Old Crow were actually naturally occurring artefacts as more became known about how predators break the bones of animals they are in the process of killing.