If the south–north and cold-adaptation theories are both correct, we have to concede that the initial physical changes may have resulted from an evolutionary mechanism other than adaptation to cold, and that some of those changes were later serendipitously amplified by cold selection.
Neoteny in humans
I am drawn to Guthrie’s explanation of evolutionary pressures in the north, but also favour an initial south–north movement on the basis of dental and genetic evidence. There is another evolutionary phenomenon that may bridge the two. An interesting hypothesis put forward by palaeontologist Stephen Jay Gould many years ago was that the package of the Mongoloid anatomical changes could be explained by the phenomenon of neoteny, whereby an infantile or childlike body form is preserved in adult life. Neoteny in hominids is still one of the simplest explanations of how we developed a disproportionately large brain so rapidly over the past few million years. The relatively large brain and the forward rotation of the skull on the spinal column, and body hair loss, both characteristic of humans, are found in foetal chimps. Gould suggested a mild intensification of neoteny in Mongoloids, in whom it has been given the name ‘paedomorphy’.21 Such a mechanism is likely to involve only a few controller genes and could therefore happen over a relatively short evolutionary period. It would also explain how the counter-intuitive retroussé nose and relative loss of facial hair got into the package.
There are several evolutionary mechanisms by which paedomorphic individuals could produce relatively more offspring over time, which could operate through drift or selection, and which are not mutually exclusive. One could be through an association with thrifty genes, useful for the cold steppe (decrease unnecessary muscle bulk, less tooth mass, thinner bones, and smaller physical size); this follows the selective/adaptive model of Mongoloid evolution, which could have made use of pre-existing traits that just happened to arise among Sundadont populations migrating up the coast from the south. Equally, paedomorphic women may have been more highly prized for looking cuter: this is more of a sexual selection and drift hypothesis and, again, while further exaggerated drift or selection may have occurred in the north, the pre-existing traits could have ultimately come from the south.
I would argue that both mechanisms came into play in Mongoloid development. Southern Mongoloid features could have developed initially as a result of sexual selection and/or drift. Then, as some of those peoples moved north into Central Asia, there would have been further ‘development on the theme’ in response to the evolutionary pressures Dale Guthrie so vividly describes. In a sense, therefore, there were two homeland platforms for the development of Mongoloid features. This armchair theory has no immediate scientific support since geneticists are, as yet, only on the threshold of understanding the genes that control growth and body moulding, let alone detecting meaningful differences within our own species. On the other hand, genetic tracking may be able to help with the direction of migration.
Four routes into Central Asia
As with all previous explorations, by both modern and archaic humans, geography and climate decided the newly arrived occupants of Asia where to go next. The rules would have been simple: stay near water, and near reliable rainfall; when moving, avoid deserts and high mountains and follow the game and the rivers. We have seen circumstantial evidence that the beachcombing route round the coast of the Indian Ocean to Australia was the easiest and earliest option. Why should this have been? It was not that easy: for a start, every few hundred kilometres our explorers would have had to ford a great river at its mouth. Yet this is just what they must have done to get to Australia, so it is possible they did the same along the East Asian coast. At each river there was the option for some people to turn left and head inland, harvesting river produce and game as they went.
As one of the earliest European explorers, Marco Polo, found out, mountains and deserts present formidable barriers to those trying to gain access to Central Asia; apart from a few trails, the only routes of entry are along the river valleys. We have seen that our first successful exodus from Africa took the ancestors of all non-Africans south along the Indian Ocean coast perhaps as long ago as 75,000 years. They may also have beachcombed as far as eastern China and Japan rather early on. They would thus have skirted the whole of the Central Asian region. They could have tried to head upriver and inland at any point on their journey.
North of India, with the Himalayas in the way, it was not as straightforward as that. The raised folds of mountains caused by India’s ancient tectonic collision with Asia extend either side of Nepal and Tibet well beyond the highest Himalayas. A vast band of mountains, all over 3,000 metres (10,000 feet), blocks Central Asia to access from the Indian Ocean coast for a distance of 6,500 km (4,000 miles) from Afghanistan in the west to Chengdu, in China, to the east. This band is rucked up like a carpet in the east, thus extending the mountain barrier south as a series of north–south ridges over a distance of about 2,500 km (1,500 miles) from the beginning of the Silk Road in northern China south to Thailand.
The Silk Road, first made famous in the West by Marco Polo, is a long trading route, parallel to and to the north of the Himalayas, connecting West with East. It passes right through Central Asia, directly along the southern edge of Guthrie’s Mammoth Steppe heartland. The Silk Road was then, as it is now, one of the few links between China and the West, if the long coastal route round south via Singapore was to be avoided.
East along the Silk Road from the west end of the Himalayas Today the Silk Road skirts both the southern and northern edges of the Taklamakan Desert of Singkiang. During the Palaeolithic, what is now desert was mostly lush grassland, and farther north a series of waterways, including the Tarim and Dzungaria rivers, provided easy west–east access for hunters from the western Central Asian regions of Tajikistan, Uzbekistan, Kirghistan, and Kazakhstan into Singkiang and Mongolia. These waterways may have been used by earlier humans to get to Central Asia.22
To look at Stone Age practicalities, let us take the first access route to Central Asia up the Indus, 8,000 km (5,000 miles) to the west of China at the western end of the Silk Road. Assuming for the moment that we are talking about an offshoot of the first Indian beachcombers, their first task after moving up the Indus would have been to negotiate the mountain barriers to the north of India and Pakistan. These extend as far west as Afghanistan. Bypassing the mountains and moving through Afghanistan too far to the west would have been difficult if not impossible, since it was near-desert. Marco Polo crossed these deserts, leaving from Hormuz at the mouth of the Gulf and passing through Afghanistan to Kashmir, crossing a high pass directly into China and the city of Kashgar, to arrive well along the Silk Road and directly in the heartland of the former Mammoth Steppe (Figure 5.5).
Marco Polo could have followed a much easier route to Kashmir, however. From the coast of Pakistan a little further to the east, the great Indus snakes northward to a point where there is a water connection through to Kashmir. Another lower-altitude route into Central Asia, also via the headwaters of the Indus, would have been to cross the Khyber Pass to Kabul, and thence to Uzbekistan and Kazakhstan, and then east towards Singkiang.
Figure 5.5 Four Palaeolithic routes into Central Asia. Access to Central Asia has always been limited by the Himalayas, their flanking ranges and various deserts. The possible routes of entry, mainly via the great Asian rivers, are shown here and apply to the following maps in this chapter and the next. Earliest human settlements also shown.
West along the Silk Road from China Equally, during all of human history, the Silk Road has been the only route west from China into Central Asia. So, an alternative route into the Mammoth Steppe would have been from the East Asian Pacific coast. The vanguard of the earliest beachcombers could have gone all the way to China and then moved west from northern China along the Silk Road into Mongolia, Sinkiang, and southern Siberia.
North into Tibet from Burma The third access route to the Mammoth Steppe, not much used by traders tod
ay, is just to the east of the Himalayas. The eastern edge of the Himalayas consists of multiple folds where the edge of the Indian plate rucked up the Asian continent on collision. We can see from the map (see Figure 5.5) that these rucks are the conduits for most of the great rivers of South and Southeast Asia. From west to east, these are the Brahmaputra, which flows into Bangladesh, the Salween, which flows into Burma, the Mekong, which flows into Vietnam, and the Yangtzi, which flows into southern China. As they flow out of south-east Tibet these four major rivers run parallel for about 150 km (around 100 miles), separated from one another by only a few kilometres. The last of the four, the Yangtzi, originates in north-east Tibet near the northern edge of the plateau and at the beginning of the Mammoth Steppe. I mention these multiple river routes not because many legitimate traders use them today, but because they allow direct access to Tibet, Mongolia, and Central Asia from any of four widely separated river mouths in Southeast and East Asia discharging on to the Indo-Pacific coast. Also, as we shall see, Tibet shares much genetically with Indo-China and Southeast Asia.
East from Russia Finally, there is another, more northerly route of migration from the West into East Asia to be considered: via Asian Russia, known as the Russian Altai. The easiest direct land access from the Russian Altai to Central Asia during the milder parts of the Late Stone Age 30,000–50,000 years ago would have been to cross the steppe directly. Travelling east through southern Siberia via a series of lakes and waterways, our ancient explorers could have reached the Lake Baikal region by a route passing north of Singkiang and Mongolia. At that time the steppe covered the whole region in greensward and open woodland. Clearly, for modern humans to have taken this route they must have got to the Russian Altai in the first place. As we shall see, they had reached both the Russian Altai and Lake Baikal in southern Siberia by 40,000 years ago.
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.
Out of Eden: The Peopling of the World Page 22
