Read Out of Eden: The Peopling of the World Online
Authors: Stephen Oppenheimer
The power of mitochondrial DNA to trace such ancient relationships was demonstrated during the making of
The Real Eve
, the Discovery documentary film based on this book. The producers decided to take a small number of DNA samples at random from volunteer Americans of different ethnicity. The mtDNA was extracted and analysed by Martin Richards in his lab at Huddersfield, West Yorkshire. Towards the end of the film is a shot of the participants being told their results (with full consent). By rare coincidence, two of the them, an American of Greek ancestry and a Native American of the Cree tribe (see
Plate 25
), both belonged to the X mtDNA clan. For a moment they stared at each other across the lab, at first silently and in amazement, then finally able to express their emotion at the realization of an ancient link between them.
How many migrant groups, and where from?
The real genetic puzzle about the origins of X in the Americas is its rarity in Asia and the linked question of where in Eurasia it originally came from. That is part of the larger problem of deciding whether the Americas were populated by single or multiple immigrations, which must be addressed first. So, before we look at how X got to both Europe and the Americas, we must look again at what the evidence can tell us about how many migrations there might have been to the Americas. But haven’t I already resolved that, by presenting the genetic evidence of all five lines entering America before the ice age, the so-called ‘one-wave and re-expansion’ hypothesis? Not so. The uncertainty associated with genetic ages is usually in terms of thousands of years. And while it is possible to use genetics to argue against Clovis-first, we cannot use genetics the other way
round to show that that all five founders entered the Americas at exactly the same time.
Looking through the genetic research on the peopling of the Americas, we can see a clear tendency, as the 1990s progressed, to reductionism, with four migrations turning to three, three to two, and finally to a single colonization of the Americas followed by a re-expansion from the same founder types. This minimalist approach is not mirrored in a rationalization of the total number of maternal American founder lines, which started at four over ten years ago and is now at least five.
By simple analogy, the five mtDNA strands that colonized the Americas are five times as many as the single African mtDNA line that colonized the non-African world; so either there was a large founding group with no genetic drift, or there were multiple entries. This does not give strong support to a single band colonizing the Americas, for the following reasons. In
Chapter 2
, I argued that the single African exodus follows logically from the single paternal and maternal African lines that parented the rest of the world. To get down to just one line, the founding group must have gone through a period of isolation and drift. This unitary argument clearly cannot be applied to the Americas. Although it is possible that the Americas were colonized by a single large hunter-gatherer group, this cannot be inferred from any of the genetic evidence, including and not forgetting the Y chromosome. The weakness in the evidence has been tacitly acknowledged by geneticists Anne Stone and Alan Stoneking, who have recently argued for a ‘single’ entry. Three lines before they postulate a ‘single wave of people’, they state disarmingly that, ‘Most likely, many small groups of people wandered across Beringia as they followed game . . .’
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But does it matter whether the single wave was composed of one or many small groups? I think it does, because one band implies, logically, there was only one geographical source. Several genetics
labs have taken the idea of a single American entry one step backwards into Asia by looking for a single Asian geographical source of Native Americans. So convinced are they that there must be one origin in Asia that they look for Asian regions that hold all five of the American founder lines.
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The idea that there can be one part of Asia that had all the right gene lines and the right Palaeolithic technology is not only naive but, as we shall see, does not fit other observations.
In any case, the genetic story told by Peter Forster and others is not of an Asian homeland. They tell us rather of a homeland in the now partly submerged Beringia, an environmental refuge which straddled the two great continents and was continuously occupied through the ice age. It was Beringia, then, that received incoming migrations from, presumably, several parts of Asia, and acted as a staging post for onward migration. The climatic conditions leading up to the LGM cut Beringia off ecologically, first from Asia (by polar desert) and then from America (by ice). Before the Americas were colonized, and before the ice sheets finally blocked the route onwards into Canada, the maternal lines in the Beringian settlements had drifted down to the five that eventually did enter the Americas. Then, during the ice age and after the Americas had been colonized, Beringians dwindled further down to just one of the five mtDNA founder lines, Group A.
We shall come back to the possible Asian and other sources of those five lines. But first, what other evidence is there that could tell us whether the migrations to Beringia from Asia was single or multiple? We have just been looking at one clear piece of evidence that tells us that the first Americans were anything but – if I may be excused for using the expression – clones from a single Asian tribe. That piece of evidence is Kennewick Man. He physically breaks the mould with his non-Mongoloid, South Pacific, and Ainu characteristics. Obviously, we can never know his skin colour or whether his
hair was dark, curly, straight, or whatever, but he was clearly different from the majority of modern Native Americans, and he was not the only early North American to be so different.
Spirit Cave Man, at around 9,400 years, is another famous ancient American, this time from the Great Salt Lake (see
Figure 7.1
). He was also different from any modern population, including Native Americans; uniquely in his case, his body had mummified and his black hair could be seen for a while before it bleached red in the light. The nearest source groups suggested for him were Ainu, Polynesians and Australians. Three other atypical Palaeo-Indians from the northern States include Pelican Rapids, or Minnesota Woman (7,800 years old and found in 1938), Browns Valley Man (also Minnesota and 8,900 years old), and Buhl Woman from Idaho (10,800 years old). We should remember, however, that not all North American Palaeo-Indians of that vintage were different from modern Native Americans. Wizards Beach Man, at 9,200–9,500 years, did resemble modern Native Americans.
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South America has its own claims for extremely old dates of colonization, and clearly was not going to keep quiet on the issue of ‘unusual’ palaeo-ancestors. Although they have been known about for some time, these skeletal reminders of the southern past came to public attention only quite recently. As with Kennewick Man, this happened through media speculation over a rather dubious interpretation of an interesting discovery. In August 1999 a BBC documentary reported that Brazilian human evolutionist Walter Neves had been studying so-called Negroid people from extinct tribes in South America. The centrepiece was the skull of a twenty-two-year-old Brazilian woman born over 11,500 years ago, nicknamed Luzia. Initially discarded and donated to the National Museum of Brazil by a French archaeologist excavating in Minas Gerais, Brazil, in the 1970s, her skull had features which suggested an Australian, Melanesian, or even African origin. In 1999 the forensic artist Richard Naeve, from Manchester University, reconstructed Luzia
and fleshed her out.
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Reborn, she looked anything but modern Native American (see
Plate 27
). Judge for yourself – we all have a claim to be innate experts in such recognition. Negroid, Australian, Melanesian, Liujiang possibly, but to me she looks just like one of the 3,000-year-old great carved Olmec heads of Central America (see
Plate 28
).
Is Luzia a remarkable link to an unknown past, or is she just one of a kind? Human variation is such that one swallow does not make a migration. More numbers are needed. A time-depth study of several ancient skulls from Serra da Capivara in north-east Brazil indicated to Neves that there was a change in skull shape around 9,000 years ago from robust-featured skulls to more Mongoloid and modern types. He speculated on an earlier migration of robust non-Mongoloid people, similar to those I referred to in
Chapters 5
and
6
as remnants of the beachcombing route. The beachcombers represented the least physically changed types outside Africa. Australian, Melanesian, Ainu, and Polynesians (and even Europeans) are all likely to be nearer to the original beachcombers than to the Mongoloid peoples of East Asia and America (see
Chapters 4
and
5
). So if there is a possibility that these non-Mongoloid types formed part of the migrations to America, appropriate comparisons have to be made. However, the best representatives of the Asian beachcombers of over 12,000 years ago are more likely to be the rather robust East Asian skulls of that vintage found in China, than today’s admixed relict groups. Neves did actually find links between the Palaeo-Indians and Palaeolithic skulls in northern China as well as South Pacific peoples.
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Unlike the makers of the 1999 BBC documentary
Tracking the First Americans
, Neves apparently did not favour the theory that these Luzia-like people had sailed to South America across the South Pacific from Australia. In his view, these robust types were more likely to have taken the same route as everyone else – either through Beringia or along its coast. He also felt that they had been replaced
or wiped out by a later influx of Mongoloid types in a separate migration into the Americas.
Are there any remnants of those beachcombers left in modern American populations? Well, there may have been until very recently. The first European explorers to reach the southern tip of the Americas noticed numerous fires burning on the land, hence the name given to that extreme region – Tierra del Fuego, the ‘Land of Fire’. The people who kept these fires burning to counter the bitingly cold wind were hunter-gatherers entirely different biologically and culturally from their neighbours and from all other known Native American groups. In the maze of waterways to the south-west, around Cape Horn, were the so-called ‘canoe indians’.
Slightly farther north were the so-called ‘foot indians’. These included the Tehuelche of Patagonia and the Selknam of northeastern Tierra del Fuego. Large, robust hunter-gatherers, their burning campfires were seen by Ferdinand Magellan and his crew as they sailed through what is now called the Magellan Strait. Many skulls of these people are in the possession of museums – the English ranchers who subsequently occupied the area placed a bounty on Selknam and Tehuelche heads when the indigenous peoples turned to sheep-raiding after their ‘free-range guanaco’ lands were taken over as sheep stations. There may only be a couple of descendants of these tribes still alive today (see
Plate 23
).
Cambridge-based Brazilian biological anthropologist Marta Lahr included a group of skulls from the historic period (twenty-nine, including Selknam and Tehuelches) in her classic study of human cranial variation.
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This group shared several features with Australians, in particular their degree of robusticity. However, apart from robusticity and its associated features, the Selknam and Tehuelches did not share much else specifically with the Australian skull morphology (e.g. non-metric traits) – and were, in particular, much larger – indicating most likely simply a shared retention of a Pleistocene trait if not a more distant relationship. Lahr was of the
opinion that these hunter-gatherers were unlike other modern Native Americans and East Asians, and more like Southeast Asians and South Pacific Islanders. She thought that these differences between Amerindians most likely indicated that there had been separate immigrant groups to America.
Recently, Walter Neves, of the University of Sao Paulo, and Joseph Powell, University of New Mexico, two of the foremost specialists in this field, joined forces in a major comparative analysis to see whether they could make sense of the accumulating evidence for Palaeo-Indians being different from, and more variable than, modern Native Americans.
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Their findings confirmed that if there were multiple founding migrations (the alternative would have to be local differentiation), Palaeo-Indians would have been more like the undifferentiated Indo-Pacific beachcomber type, while modern Native Americans are more like Northeast Asians, and also have affinities with Europeans. Furthermore, they argued, North American Palaeo-Indians were different from South American Palaeo-Indians in that the former strongly resemble Polynesians, while the latter are more like early Australians. They did not accept the latter as evidence of a direct migration across the South Pacific. Instead, like Lahr, they argued that both Australians and Southern Palaeo-Indians derived from a common ancestral source on the Asian mainland.
Such a picture of multiple separate morphological affiliations between different American groups (ancient and recent) and different Asian/Oceanic types is consistent with at least two, and possibly three or more, separate migrations from different Asian regions, with the Mongoloid type eventually expanding largely to replace Palaeo-Indian types.
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We can definitely fit this in with the emerging genetic consensus of Beringia as the homeland, acting as a staging post for inward migrations of different peoples from various parts of East Asia.