Out of Eden: The Peopling of the World (33 page)

We have now seen that there are four possible access routes into Central Asia: three from the Indo-Pacific coast (west, south, and east) and one from Russia (north-west). Once in Central Asia, there were three parallel routes along water bodies between East and West Asia which the pioneers could have followed: two southern ones, through Singkiang and Mongolia, and a northern one across Southern Siberia. The northern route would have been accessible only during the milder periods of the Palaeolithic 30,000–50,000 years ago, during the interstadials (see
Chapter 3
).

When did modern humans first roam the steppe?

At present, it is along the last and most northerly of these three corridors that we find the clearest archaeological evidence for modern humans north of the Himalayas over 40,000 years ago. Southern Siberia is right at the northern reaches of Guthrie’s favoured Mammoth Steppe heartland of Singkiang and Mongolia. Exciting recent excavations in the caves of U’st-Karakol and Kara-Bom in the Russian Altai (see
Figure 5.5
) indicate that the new Upper Palaeolithic stone technology had arrived there by 43,000 years ago. These Altai dates are closely followed, farther to the east, by a 39,000-year-old Upper Palaeolithic site at Makarovo on the western side of Lake Baikal. By 30,000–35,000 years ago, more such sites appear at Varvarina Gora and Tolbaga on the eastern
side of Lake Baikal, and at Malaia Syia, much farther north near the Yenisei River. This means that the Upper Palaeolithic transition across southern Siberia was at least as early as that in Europe.
²³

Belgian archaeologist Marcel Otte has recently suggested a centre of origin for the Upper Palaeolithic technology in the northern Zagros Mountains of Iran and Iraq from where it spread both northwest to the Levant and Europe, and north-east into Central Asia and the Russian Altai, presumably either along the route just described for Marco Polo or through the Caucasus first.
²⁴

Can stone tools tell us which human was the first in Central Asia?

The appearance of Upper Palaeolithic technology has been accepted as the definitive signal of modern humans’ first entry into Balkan Europe further to the west, and has been used to distinguish their movements from Neanderthals who had been making Middle Palaeolithic tools there for several hundred thousand years (see
Chapter 3
). This could suggest a parallel arrival of modern humans sharing the same Upper Palaeolithic technology into the Altai by at least 43,000 years ago from the Zagros region to the south.
²⁵
However, if Upper Palaeolithic technology is not a
sine qua non
for moderns in Asia, then modern humans might actually have arrived even earlier in the Russian Altai.

There are several reasons for this caution in dating modern arrivals anywhere in Asia. First, although the Upper Palaeolithic stone technology uniquely confirms the presence of modern humans in Europe, as we have seen for the Levant and Southeast Asia, it was not the only technology used by moderns so it cannot help us to define their first arrival elsewhere. The Upper Palaeolithic was a collection of innovations, the first of which appears in the archaeological record 45,000–50,000 years ago and is particularly associated with North and West Eurasia. Early modern humans used several different older techniques, including similar Middle Palaeolithic traditions to those of the Neanderthals. The caves in
the Russian Altai, in particular Kara-Bom, also show a Middle Palaeolithic tradition underlying the Aurignacian Upper Palaeolithic layers and dating back as far as 62,000–72,000 years ago. These lower layers are difficult to assign to either modern or archaic humans (such as Neanderthals), since they could have been made by either and there are no fossils available to identify their makers. No Neanderthal remains have ever been found as far north as the Russian Altai, although they have been found much farther to the south-west, in Teshik Tash in Uzbekistan, Central Asia. A key issue is whether the older Middle Palaeolithic layers show a continuous indigenous graded change towards the later technology, or the Upper Palaeolithic is intrusive. The latter seems to be true, at least for the Aurignacian technology. So the possibility remains that the earlier Middle Palaeolithic, going back 60,000–70,000 years in the cave of Kara-Bom, represented an even earlier modern human occupation of the Altai.
²⁶

The second reason for caution is that, until recently, the timeline of the Palaeolithic record of Singkiang, Tibet, and Mongolia to the south has hardly been studied. This is not for lack of Palaeolithic remains, but at least partly because many of them have not been datable. A recent field report from Mongolia suggests a Middle Palaeolithic tradition going back perhaps 60,000 years. Another report suggests two separate Upper Palaeolithic (microlithic) traditions in Tibet, a northern and a southern one, which were linked respectively with peoples and stone-tool traditions of northern and southern China. Dating was uncertain, since many finds were on the surface (surface finds lack context and stratification, which are essential in the process of archaeological dating).
²⁷

So, there is very clear archaeological evidence for an Upper Palaeolithic technology spreading parallel but farther north right across southern Siberia, starting from the Russian Altai 43,000 years ago. On the other hand, there was an earlier human occupation of Central Asia and the southern heartland of the Mammoth Steppe,
but there is as yet no clear fossil evidence for their identities. As we shall see shortly, the genetic evidence from North Asia supports the 40,000-year date for the arrival of modern humans in north-west Asia. The North Asian Upper Palaeolithic eventually shared the rich Mammoth-based Gravettian culture of Central and Eastern Europe farther west, as can be seen from art discovered at Mal’ta near Lake Baikal from 23,000 years ago (see
Plate 21
).
²⁸

Genetics

I have reviewed archaeological evidence which supports the presence of early modern humans in Central Asia and for their presence at the three entry points from the coast to the only corridors into Central Asia, the Silk Road and Guthrie’s Mammoth Steppe heartland. These three entry gates were in north-west Asia, Indo-China, and north-eastern China. So far I have mentioned little about the genetic evidence – and there is a reason for this. The tree structure of the mtDNA and Y markers is better at signalling ancient migrations of molecules than it is at dating movements or identifying so-called ‘races’ or ethnic groups. It is therefore safer, where possible, to identify what migration routes are allowed by geography, archaeology, and climate before testing how these are supported by the genetic story.

A clear north–south division in East Asia

I said in
Chapter 2
that after the initial modern human dispersals out of Africa, each region of the Old World and the south-west Pacific became settled, and little if any further inter-regional gene flow happened until the build-up to the last great glaciation 20,000 years ago. Asia, in spite of its history of mass movements, is no exception to this rule. Certain broad genetic divisions within Asia became clear to geneticists before the focus on mtDNA and Y markers. As expected, the Caucasoid regions of West Eurasia were found to group together, with some overlap on the Indian subcontinent.
There was a clear separation from East Eurasia, which in turn split north–south, consistent with the Northern and Southern Mongoloid division. In terms of human provenance, we can thus distinguish between Southeast Asia (including the south coast of China: Guandong, Guangxi, and Fujian provinces) and Northeast Asia (including northern China, the east coast of China, Korea, Mongolia, Tibet, and parts of Siberia), with one group in the extreme north-east of Asia intermediate between the Caucasoids and Northern Mongoloids.
²⁹

Such studies have not helped much to trace origins, but they do serve to show that there are still marked regional differences, even among the majority so-called Han ethnic group in China, who also show a clear north–south difference. These studies also bury some myths that have grown up about Chinese genetic origins. For example, it had been widely accepted that there was a massive population expansion of Han Chinese from north to south during the past several thousand years of Imperial rule, overlaying, displacing, and replacing the bulk of indigenous minorities in the south. Recent historical research has shown, however, that Han identity in the south of China was, for pragmatic political reasons, adopted or even synthesized by southern indigenous peoples over the past few hundred years.
³⁰
This suggests that much of the historic population migration in China was apparent rather than real, and supports the view that regional populations may have been more stable over the past few thousand years than was previously assumed.

Another approach to the question of whether Mongoloids originated in the north or the south is to consider diversity. On general Darwinian principles, a new species (or, in this instance, new ethnic group expanding from a small founder population) should have one centre of origin, which should retain the greatest diversity of types (e.g. genetic) within that group. Now, whichever genetic system one uses, Southern Mongoloids always show far greater genetic
diversity than do those in the north. Y-chromosome evidence has already been used to justify placing the Mongoloid homeland in the south.
³¹
Although it is useful, we face two potential pitfalls if we take such a simplistic diversity approach. First, none of the gene lines or markers used has been clearly identified as ‘Mongoloid’: they are simply Mongoloid by implication because of where they have been found, so the argument is in danger of becoming partly circular if it is crudely applied. Second, North Asia, unlike tropical Southeast Asia, would have suffered depopulation, great extinction, and genetic drift during the last glaciation, so the low diversity would be expected in the north today and thus may not necessarily reflect the original picture.

An extreme hypothetical view of the effect of the last glaciation on Central and North Asia is that the entire Asian region extending north of the Himalayas was completely cleared of people, so that today’s populations are merely re-entrants from South China and Southeast Asia and from Europe. That would of course mean that we can never know the original genetic composition of Northern Asia. This view is not tenable. First, palaeoclimatological studies show that during the ice age extensive steppe tundra regions persisted in Central Asia which could have supported hunters. This is backed up by archaeological evidence for continuous occupation through the last glacial maximum (see
Chapter 6
). Dale Guthrie certainly argues against such a complete extinction in the south of the Mammoth Steppe heartland. Second, as we shall see, this picture fails to explain the deep genetic diversity of south-west Central Asia (Uzbekistan and Kirghistan), or the marked geographical difference in deep genetic branch lines between north and south Asia. In particular, as I shall show, there are a group of lines still shared uniquely between northern Europe, northern Asia and northern America that have no links at all with south China or Southeast Asia.
³²

Mapping the spread of the gene tree

As with the out-of-Africa story, the answer becomes clearer when we look at the Adam and Eve markers. The great advance that came with the mapping of the mtDNA and Y-chromosome trees was the ability to trace individual molecular branches and their twigs, like a vine, from one region to the next. The fancy name for this tracking game is phylogeography, but at its simplest it consists in following twigs back to their branches and connecting points on a map.

The rules are simple, although their application can be complex. To detect a migration from one region to another, we need to find the source branch type in both regions and a new unique twig in the target region that is not present in the homeland. For a homeland with multiple migrations in different directions, we need to identify common branches in the homeland that have
different
unique twigs in the other regions. Perhaps one of the best known and earliest examples of this approach was published by Italian geneticist Antonio Torroni and his colleagues in 1993. They identified four American founder mtDNA lines, which they labelled A to D. Each of these four bushy twigs, although showing unique new sprouts in America, could be traced back to the equivalent source branches, A, B, C, and D, in Asia (see
Chapters 6
and
7
).