Out of Eden: The Peopling of the World (48 page)

In contrast to these four maternal lines, which have a more northerly distribution today, the B maternal group clearly has her origin and place in the south. Group B dominates Indo-China, Southeast Asia, and the Pacific, and has a very different world distribution from the northern lines. Although B is found in Japan, China, and Mongolia, she is absent from the Subarctic regions both in Eurasia and North America. This makes a strong case for the source population of American Group B having been very different from C or X.

There are further constraints on the origins of Group B. In Asia, B is represented by two main branches, B4 and B5, found side by side in most regions except the Americas and the South Pacific, where only B4 is found. B4 is the only branch that got to America, and she also dominates the South Pacific. The B4 branch in East Asia is so huge, varied, and widespread that it would be like looking for a needle in a haystack to search for an Asian match for the precise American founder type. But by coincidence, there is a near match from the recent results of two independent, complete mtDNA sequencing studies, one conducted by geneticists in Japan and the other by geneticists from Sweden and Germany. This laborious method, rather like a mini Human Genome Project, on just one stretch of DNA, goes for complete sequencing of the whole, circular mtDNA molecule. The result is the most precise and specific maternal genetic fingerprint possible. The match I found when comparing these two studies was between a Piman Indian Group B4 and a Japanese Group B4, thus pointing to the Asian Pacific Rim coast as the source for at least one American B type. The matches are strong, although as expected they are not like identical twins, but they do exclude the rest of the deep branches of Asian B4 and they do establish a link between Japan and America (see
Figure 7.7
).
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Rainbow coalition

Arguments based on finding individual near matches cannot accurately identify multiple different Asian homelands for the five American founder lines in Asia any more than the process of looking for a region, such as Mongolia, which harbours A, B, C, and D can identify a sole American homeland in Asia. They do, however, show us a more open-minded view of the possible events leading up to the peopling of the Americas and the potentially diverse sources of that colonization. We saw in
Chapter 6
how the archaeology of the Asian Pacific coast bears signatures of new incoming Upper Palaeolithic technology from the Eurasian steppe in the west, and probably also microblade cultures from Tibet and the Qinghai Plateau, during the build-up to the last ice age. These may well have represented refugees from Caucasian populations to the west and from a Mongoloid source farther south. Arriving in north-east Asia, Korea, and Japan, they may have found themselves rubbing shoulders with the older coastal East and Southeast Asian peoples who were descended from the beachcombers (and represented today by the Ainu). So there were possibly as many as three different-looking groups that moved north-east along the coast, living off the rich marine life and game. They and their diverse cultures, genes, and physiognomies would all eventually have arrived in Beringia.

Wandering separately

What might Beringian communities have looked like on the eve of their entry into Alaska, 22,000–25,000 years ago? Were they like
Star Trek
’s Star-Base 9, polyglot, polymorphic, and polychromatic? In other words, were they completely mixed communities? I do not think so. Beringia was huge, with a variety of resources and locales to offer different cultures. It is more likely that, in spite of inevitable mixing, some of the cultural and genetic diversity was preserved in separate ethnic groupings.

When those groups ventured into the Americas and fanned out and multiplied, they did not proceed like some consolidated, multiethnic United Nations team. The cultures which sprang up when the newcomers put down roots in the New World preserved separate and unique physical, genetic, and cultural elements from the various Asian homelands. Is this picture supported by the archaeological evidence? I think so. The search for pre-Clovis artefacts turned up implements beneath the Clovis layers and in the early non-Clovis sites of North and South America which were from completely different traditions and had different analogues on the Asian side. This is just what we would expect from several parallel colonizations by different cultures.

We might expect, given the varied physical appearance of early American communities, to see clear genetic differences between them. Such differences are there in the marked tendency for tribal differentiation in mtDNA subtypes as noted by Torroni and Wallace (see above); yet one of the arguments for a single colonization of the Americas has always been the finding of A, B, C, and D major groups present in North, Middle, and South America. The Americas are huge, however, and there are marked differences in the relative frequencies of the five founders across different American peoples.

Present-day ethnic groupings are distinguished by particular tribal-specific mtDNA types. With certain exceptions, there is little sharing of individual mtDNA types between ethnic groups. This has been interpreted to mean that the single founding wave quickly split up into groups that remained separate and drifted to different frequencies of founders. But the evidence equally fits the alternative picture of the first wave of colonization containing multiple discrete genetic strands which can be traced all the way back, through Beringia, to different Asian sources. We have already seen the most extreme cases in the Subarctic region, where the Na-Dene speakers of Alaska and the north-west coast only have Group A2 American
maternal types. As we have seen, the reason for the single American A2 line in the Na-Dene and Inuit-Aleut is thought to result from the near extinction of their ancestors causing drift down to one line.
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This extreme predominance of Group A extends throughout northern America north of the 50th parallel, and includes not only the Na-Dene and Inuit-Aleut but also the Amerind, Algonquian-speaking northern Ojibwa of Canada and the Great Lakes. Their Group A is characterized by three unique types not found anywhere else. Not only that, but the Ojibwa have the highest rates of the rare X type at 25 per cent (see
Figure 7.3
), and have the unique honour of having only the dominant Y founder rather than its commoner derivatives. Although they speak an Amerind language, the Ojibwa share their Subarctic location and even some northern cultural features with the Na-Dene speakers. Their unique but relatively diverse genetic make-up contains a high rate of true founding lines. This suggests that the Ojibwa and related groups, rather than being a population which nearly became extinct during the ice age, as happened to the Na-Dene, may through their northern isolation have preserved a particular genetic identity deriving from their Beringian source, and ultimately from north-east Asia.
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The two Native Americans who volunteered, along with others, to be sampled in the film (
The Real Eve
) associated with this book (see
Plate 25
) were from the Great Lakes region. By some extraordinary coincidence, each had one of these unique and uncommon local types. Our Ojibwa participant had the rare A1 type, while our Cree participant (Cree also belongs to the Algonquian language group) had an X type, which had previously been found only in Northern Ojibwa people.
⁷⁴

The overall distribution of the founding maternal group A shows a clear decline from near 100 per cent in Subarctic North America to generally low frequencies in South America. The more detailed picture of A in the rest of North America is one of great variability,
between zero and high frequency. Several studies of ancient DNA in the Americas have revealed peoples completely lacking in Group A, suggesting that the older picture was one of even greater differences. A northern example was the Fremont cultures of Great Salt Lake, while another was in the extinct Fuegan tribes of the tip of South America (discussed earlier), who had only C and D.
⁷⁵

The distribution of X, as we have seen, is an exaggeration of the A picture in Amerinds, as X is confined to two ethnic groups in the far north of North America. Group D, however, is found at low frequencies in North America but very high frequencies in South America, in particular the equatorial region.

In summary, the extreme variation seen in the regional frequency of the five founder lines throughout America, could support a view of separate ethnic strands in the original colonization (although there are other explanations).

A west-coast route into America?

I have left the distribution of the most interesting mtDNA group, B, to the end. As we have seen, Group B is absent above the 55th parallel but present in North, Central, and South America. This odd southern distribution has often been put forward as proof that B arrived in the Americas along with the other lines and before the ice age. While I agree with these arguments, there is still a question mark over the exact age of Group B. Torroni found B to be significantly younger than A, C, or D; in Forster’s re-analysis, B remained younger in Central America. She is old in South America, where she has a very variable frequency, from 0 to over 70 per cent. While these discrepancies in age and distribution may be just the effects of inadequate sampling, bottlenecks, or drift, there are several other intriguing possibilities. For example, Group B4 is extremely common and diverse in East Asia. So more than one B4 colonization at different times by related twigs might not be
obvious in the American genetic record without more detailed sequencing.
⁷⁶

Alternatively, B4 may indeed have been a separate or last-minute entry to the Americas after A, C, D, and X. This is what the Russian geneticist Yelena Stariovskaya suggests. Her argument is that, apart from the younger age of Group B, she has high frequencies in Central America and in regions where Clovis tools are found, and is absent from the far south of South America. Group B is absent from Ne-Dene-speakers of the Subarctic west coast (see above), but present amongst Amerind speakers farther south. Perhaps to explain her absence from the Subarctic and the problem of the ice barrier, Stariovskaya also suggests that B came in separately along the west coast of North America. Given that there is at least one close B4 match for a Piman Indian B4 in Japan, further complete mtDNA sequencing studies on samples from both sides of the Pacific would be the way to answer these questions (see
Figure 7.5
).
⁷⁷

The idea of a coast-hopping fast migratory track from Beringia and down the west coast of the Americas has a respectable vintage and is coming back into fashion. First raised thirty years ago by Knut Fladmark of Simon Fraser University, British Columbia, the idea is an attractive explanation for the rapid colonization of South America. The problem has always been lack of evidence. Most of the beaches such a hypothetical migration would have used are now well beneath the sea. Only coastlines where there is a steep continental drop-off would be less affected by sea-level changes. Two sites on the southern Peruvian coast, Quebrada Jaquay and Quebrada Tacahuay, have just that. The bones of butchered birds and fragments of seashells (clams and mussels), crustaceans, and anchovies tell the story of sophisticated fishers and beachcombers exploiting the South American coastline 11,000 years ago at the same time as the Clovis hunters were valiantly trying to extinguish all northern big game. Evidence is also emerging from the North American west coast of human occupation and beachcombing at the same time.
⁷⁸

Some of the evidence for the viability of this now-submerged route soon after the LGM comes from another large mammalian omnivore, the bear. UCLA biologist Jennifer Leonard and Alan Cooper, New Zealand specialist in ancient DNA working at Oxford University, have been tracing North American brown bear mtDNA, both modern and ancient, to see what happened to bears in Alaska and the north-west coast at the time of the big freeze.
⁷⁹
There are close mtDNA analogues between brown bears of parts of East Eurasia and the USA, suggesting that Eurasian brown bear mtDNA lines entered Alaska through a preglacial corridor via Beringia. Bears are known to have persisted both in Beringia and on Prince of Wales Island, off south-east Alaska, through the LGM, although like humans, their diversity became reduced.

Before the LGM there were no brown bears in southern Canada, but they had spread across there by 13,000 years ago. Their mitochondrial group suggests that they arrived there, not from Alaska through the ice corridor, or by re-expansion from Alaska after the melt, but from refuges on west-coast islands. As near extinction loomed, some bear clans must have moved from Alaska down the west coast, where they have survived to the present day. What is key about the brown bears now in the Canadian and US Rockies is that their particular mtDNA clan belongs to a line that was in Alaska 35,000–45,000 years ago and is now extinct there. In other words, they expanded from an ancient Beringian resident population. Since bears and coastal humans have an omnivorous diet that overlaps considerably, the bear story may be pointing us to the route that could have been taken by humans 12,000–15,000 years ago.

Human remains and artefacts on Prince of Wales Island have been dated to 9,300 years ago and earlier. Some 3,200 km (2,000 miles) to the south, Jon Erlandson has unearthed evidence of beach-combing dating to perhaps 11,600 years ago in Daisy Cave, on San Miguel Island in the Santa Barbara Channel, southern California (see
Figure 7.1). Clearly, to cross the 40 km (25 miles) from the mainland to the island, some form of craft must have been used. Radiocarbon tests from a woman’s bones found on nearby Santa Rosa Island give her age as 13,000 years.
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