Lone Survivors (38 page)

After suffering colder and drier conditions, the climate in southern Asia improved with the temporary return of a strong summer monsoon about 57,000 years ago, and this may have helped the survival and migration of modern humans across India toward southeast Asia and Australasia at this time. However, signs of “modern” traits such as symbolism and complex technology are hardly apparent until after 45,000 years ago—a subject we will discuss later in this chapter in connection with Australia. And the Indian subcontinent does not have a single human fossil to record who was making its Middle Paleolithic tools; there is nothing between the archaic-looking braincase from the Narmada River gravels, which is probably over 300,000 years old, and fragmentary modern specimens from sites in Sri Lanka, dating from less than 40,000 years ago.

Work led by the archaeologist Michael Petraglia demonstrated there are Middle Paleolithic tools in Indian sites immediately before and some time after the widespread deposition of the Toba ash about 73,000 years ago, suggesting that whoever those people were, they may have been able to bounce back and repopulate after the apparent destruction wrought by Toba. Petraglia believes they were probably modern humans, perhaps descendants of groups like those known from Skhul and Qafzeh farther west, but if so, their mtDNA and Y-chromosome DNA have not survived today. This is because the M and N mtDNA haplogroups that exist throughout the region are probably younger than 60,000 years, while all Asian Y-DNA is even younger than this. So if these early Indians were modern humans (which is not yet demonstrable), they either became extinct or were largely replaced by later waves of modern human dispersal.

Recent DNA analyses showed just how remarkable was this spread of modern humanity across southern Asia. Study of some 55,000
single-nucleotide polymorphisms
(
SNPs
—individual “spelling mistakes” in the genetic code) in about 2,000 people representing over seventy populations from right across Asia demonstrated that, despite clear physical differences in appearance, skin color, and stature, the inhabitants of east and southeast Asia, including so-called Negrito peoples in the Philippines and Malaysia, are essentially one family of humanity (give or take some Denisovan DNA!) and derive from a single southern migration into the region. Genetic variation within the local populations decreases from south to north in east Asia, so subgroups moved north to found the less diverse populations of northern China, Korea, and Japan. However, the distinctiveness of central Asians suggests that they derived from a separate peopling of that region through the Eurasian Steppes. But groups like the aboriginal inhabitants of Hokkaido Island in Japan—the Ainu—were apparently not included in the analyses, so their origins in an even earlier dispersal of moderns, and a relationship to the first Americans, remains a possibility.

Map showing later human sites.

Map showing later human sites in Europe.

An intriguing and separate study investigated another SNP variant in Asian peoples called EDAR T1540C, and shows how DNA analyses are revolutionizing our understanding of human variation and how quirky some of our “racial” features may turn out to be. Many Asians are characterized by a hollowing on the back surfaces of their upper incisor teeth, called shoveling, since the inside surface resembles a tiny shovel—and a similar shape is also found in
Homo erectus
and Neanderthals. East Asians are also generally characterized by having straight and coarse black hair. The EDAR gene codes for proteins that are involved in the development of hair, teeth, and other derivatives of our skin and harmful mutations cause a condition called ectodermal dysplasia, where individuals may completely lack hair, nails, sweat glands, and normal teeth. The T1540C variant seems to be related to the production of both shovel-shaped incisors and coarse black hair, and is very common in East Asians, while it is virtually absent in Europeans and Africans. As yet it is unknown what produced the high frequency of this gene in East Asians. Was it chance or was it selection for one aspect—perhaps resistance to a skin disease, a particular kind of tooth strength, or thicker hair to protect against the cold, encourage the attentions of the opposite sex, or discourage the attentions of lice? Whatever the reason, it shows how features that have been considered very important in “racial” and even evolutionary studies may derive from quite unexpected factors—or no factors at all, other than as a by-product of something completely different!

An offshore core from the southern South China Sea records warm conditions and increased summer monsoons between 50,000 and 40,000 years ago, so early moderns who had arrived in the region by then were able to disperse northward under mild rather than glacial conditions—and this was probably the origin of the isolated Tianyuan modern human individual discussed in chapters 3 and 4. These East Asian pioneers were also able to move southward and reached Niah Cave in the Malaysian province of Sarawak, on the island of Borneo, by at least 45,000 years ago. This enormous cave, famous for its birds' nests which are used for the oriental soup, was partly excavated by Tom and Barbara Harrison more than fifty years ago and produced a wealth of archaeological material of different ages, but the most famous find was the “deep skull” of a modern human. This was controversially radiocarbon dated to about 40,000 years ago from associated charcoal, but many scientists refused to accept the validity of the determination, and it has taken until now for renewed excavations to show that the Harrisons essentially got it right. Moreover, the new work, led by the archaeologist Graeme Barker, showed that these early modern inhabitants of Niah had adapted quickly to the considerable demands of survival in tropical forests, since they were hunting many arboreal species and were processing local plants for their carbohydrates and others for dyes and pigments. However, their stone technology (and apparently their use of other local raw materials) was relatively simple—yet it clearly did the job very well. This reminds us of the important fact that being a modern human is as much about expediency and pragmatism as it is about harpoons, pendants, and cave art.

That is a crucial point to bear in mind as we trace the modern human diaspora toward Australia, because there we will search largely in vain in the earliest archaeological records for the markers of behavioral modernity that we have been discussing so far in this book. Evidence for complex stone or bone technology, structured sites, and symbolic behavior is generally lacking, although, to be fair to the earliest Australians, we already noted that the two 42,000-year-old Mungo fossils may represent the oldest red ocher burial and cremation so far discovered. To get there at all, these early Australians had island-hopped quite rapidly on boats or rafts across many stretches of open sea—the first long-distance seafarers of which we know—assuming, that is, that the ancestors of the Hobbits of Flores had got to that isolated island by accidental rafting rather than purposeful navigation.

The oldest known red ocher burial: Mungo 3 from Australia.

Yet the archaeological record suggests that the earliest Australians lived in small, highly mobile bands and exploited quite a narrow range of plant and animal resources, all of which could be obtained with simple technologies. The stone tools were much more like Middle Paleolithic ones than those we know from the Later Stone Age of Africa or the Upper Paleolithic of western Eurasia, and this led to the earlier suggestion that Australia was first colonized more than 60,000 years ago, before the development of the full suite of “modern” behaviors. However, from the latest dating analyses and genetic studies, it seems difficult to find evidence of colonization much beyond about 45,000 years. Although remembering the apparent simplification of life in Tasmania that followed isolation and decline in numbers, we can see how the same effect could have operated quite severely 50,000 years ago, as small numbers of pioneers survived the hazards of seafaring to reach New Guinea and Australia for the first time, and spread at low density around a vast and challenging continent. Yet in contrast, after 12,000 years ago, when native Tasmanians were apparently suffering a decline in numbers as the Earth warmed up, their mainland fellow Australians were increasing in population density in many regions.

As the archaeologists James O'Connell and Jim Allen pointed out, during the early part of the present interglacial, mainland aborigines underwent their own “Human Revolution,” developing new ways of managing habitats, increasing technological complexity, and engaging in elaborate art and ornamentation, including of their bodies. At the same time there is evidence of a tremendous increase in the number of archaeological sites in regions like the Murray River, so this brings us back to the critical question of population density: was the benefit of increasing numbers the same as we postulated for the later Middle Stone Age of Africa, with greatly increased contacts, exchanges, and symbolic signaling between groups? And was the apparent lack of the signals of modernity in Australia before 12,000 years ago a parallel with the situation in Tasmania after that time, as shrinking and increasingly isolated bands of Tasmanians shed all but the essentials they needed for survival, while indisputably still representing “modern” humans?

This brings us back to the importance of climate, for, as O'Connell and Allen point out, the productivity of Australia was probably much reduced during cooler and more arid phases of the last 50,000 years, while the peak of warmth in the early part of our present interglacial, plus its relative stability, allowed mainland populations to thrive. And it remains possible that population densities (and hence the potential to express and accumulate signals of “modernity”) fluctuated in Australia between 12,000 and 45,000 years ago. Perhaps the well-watered Willandra Lakes of 40,000 years ago allowed a temporary growth in numbers that catalyzed flashes of the expressions of “modernity” there—such as the exploitation of aquatic resources, red ocher use, and complexity in disposal of the dead.

This gives us an interesting thought-experiment to finish on, using that wonderful episodic memory of ours, before we move on to consider both the past and future of our species in the final chapter. We judge what it is to be human by the standards of our species, as we are the only surviving example available to study in detail. We are large-brained, fully bipedal, small-toothed, and good with technology (give or take an inability to work remote controls or mobile phones properly), and those are features we share to a greater or lesser extent with our extinct relatives in the genus
Homo
, such as
Homo erectus
and
Homo heidelbergensis
. But because people like the Neanderthals did not make it to the present day, we are the only surviving example of a “modern” human, so we look back at our evolution and assess “modernity” in terms of the development of “our” features: a high and rounded skull with a small brow ridge, large parietal lobes in the brain, narrow hips, and a bit of an obsession with religion, sex, and fashion (although not in my case, of course).