Lone Survivors (37 page)

There is another potential benefit of religious belief, and that is the mnemonic (from the Greek for “memory”) structures that religious myths can provide, structures that facilitate the storage and transmission of important information about the group, its history, and its environment. This is most powerfully demonstrated in the Dreaming creation myths shared by many native Australians. The Dreaming tells of the journeys of ancestral beings, animal or human, who molded the landscape and its individual features. These creator beings also passed down social rules and rituals for the maintenance of the land and the life it supports, and their journeys are marked by networks of Dreamtime tracks, joining sacred sites associated with these ancestors. One particularly widespread myth is that of the Rainbow Serpent, a huge snake that lives in the deepest waterholes, and which was born from an even larger snake marked by the Milky Way. It can manifest itself as a rainbow or can move through rivers, shaping the landscapes and singing about the places it has made. It may eat, drown, or infect those who displease it, while the righteous may be blessed with powers to heal or make rain.

In the often hostile landscape of Australia, the transmission of Dreamtime myths through the generations must have saved many lives, since the stories provide the equivalent of an outback sat-nav, leading people to waterholes, food, shelter, and natural resources like stone and pigments. Intricate legal, kinship, and territorial systems are also built into the local variants of Dreamtime, so aborigines carry a virtual guide to life in their heads, with segments of the stories recorded in paintings or carvings, and sung or acted out at ceremonies marking the important stages of life and death.

Dreamtime is a particularly all-encompassing creation myth, and probably took many millennia to reach its present levels of sophistication, but less elaborate versions of such stories and mnemonic systems probably existed in the Upper Paleolithic of Europe. Intricate carvings on mammoth tusks from some of the Danubian Gravettian sites we discussed in chapters 5 and 6 may well be maps of rivers and the surrounding lands, while a 14,000-year-old engraved block from Abauntz Cave in Spain was interpreted as showing mountains, rivers, and lakes, with herds of ibex. Whether that is true or not, it seems likely that symbols, ceremonies, and rituals acted like the Dreamtime stories in transmitting the oral history of Paleolithic societies and reinforcing their rules of life and their relationship to the landscape, even as far back as the Middle Stone Age of Africa. It is sad for many reasons that the surviving Khoisan (Bushman) peoples now occupy only a fraction of the range and environments that their ancestors did, to judge from the evidence of DNA, archaeology, widespread cave art, and linguistics. As we saw from the lessons of Tasmania, their decline in territories and numbers must have affected their cultural diversity, and we have thus lost the rich cosmological contexts that must have lain behind their traditions of cave art, which stretched back deep into the Later Stone Age. Similarly, the meanings of the enigmatic Bradshaw paintings in the Kimberley region of northwestern Australia are lost to us, since they represent a now-vanished artistic tradition on that continent.

Returning to the Middle Stone Age, I want to look at the climatic record of that period, to see whether it holds clues to the growth of modern human populations and their innovative behaviors. When I was a student, the general view was that when Ice Ages hit Europe, Africa had a wet
pluvial period
, characterized by rises in lake levels. Similarly, when Europe enjoyed a warm interglacial, Africa suffered a dry interpluvial stage, with the spread of deserts. When I coauthored
African Exodus
thirty years later, in the 1990s, I proposed that a population crash in the severe global cold stage that lasted from about 130,000 to 200,000 years ago could have been the catalyst that drove the evolution of
Homo sapiens
in Africa. However, we now know that global climates are not read so simply, and climatic change in Africa often danced to a different rhythm from that of the major Ice Ages marked in expanding ice caps and falling sea levels.

In fact, different parts of Africa are affected by different factors. Studies of river and lake systems and of desert dust and pollen in offshore sediment cores show that varying conditions in the North Atlantic (for example, the chilling effects of Heinrich events) clearly influenced North and West Africa. However, the East was affected by the changing patterns of the monsoons off the Indian Ocean, while South Africa was influenced by conditions in the Southern Ocean, adjoining Antarctica. At times there were windows of opportunity for humans, with well-watered conditions in parts of Ethiopia 195,000 and 160,000 years ago, at Omo Kibish and Herto respectively, but the latter period was probably much more severe in the south, with sites like Pinnacle Point providing refugia near the relative stability of coastal resources. As we saw, during the warm interglacial about 120,000 years ago, the Sahara was “greened,” with lakes and river systems, and the expansion of gallery forest and grasslands, favoring the spread of Aterian hunter-gatherers, with their distinctive tanged spear points, shell beads, and red ocher. But climatic data farther south suggest that central and southern Africa were generally more arid then, with many rivers and lakes suffering fluctuating levels, or even drying out completely. But after 75,000 years ago the situation reversed, with the Sahara turning to desert most of the time, while farther south much of Africa entered a cooler but more humid phase, with substantial rises in many of its lakes and river systems.

Human population sizes would thus have ebbed and flowed in Africa, sometimes extensive by ancient (but not modern) standards, and potentially in contact even across the full extent of what is now the Sahara, at other times pinned back in isolated refugia like Herto and Pinnacle Point. The complex climates of Africa may also explain why there seems to be no single center of origin for the earliest signals of behavioral modernity. Perhaps North Africa (and the Middle East?) led the way 120,000 years ago, but as conditions deteriorated, populations there shrank back or even became extinct, as favored environments rapidly vanished. Perhaps the torch of modernity was then kept alive farther south at sites like Blombos and Klasies River Mouth, as conditions favored that region for a while (give or take the interruption of events like the Toba eruption). Waves of population expansion and contraction could explain the brief but extensive florescence of the Still Bay culture with its rich symbolism, and the subsequent rise and fall of the Howiesons Poort with its innovative tiny hafted blades and engraved ostrich eggshells (recently described from Diepkloof rock shelter) more than 5,000 years later. And it is my guess (though we lack much data to support it) that East Africa became one of the next centers for behavioral evolution, about 60,000 years ago, as it was from there that modern humans (and their developing suite of modern behaviors) made their way out of Africa. My work with three geneticists on the recalibration of mtDNA evolution, discussed in the previous chapter, suggested that this was also the time of origin and first expansion of the L3 haplogroup, which gave rise to the M and N haplogroup families that characterize all of humanity outside of Africa.

So what can we say about the factors that led to the main modern human exodus from Africa about 55,000 years ago (assuming the earlier spread to regions like Israel was only a temporary range extension from Africa)? When considering movements of humans in ancient times, we usually take into account two factors—simply expressed as push and pull. The former is caused by negative factors, forcing groups to move as a result of a lack of resources, drought, or overpopulation. The latter is caused by positive factors such as the expansion of a favored environment or the promise of rich resources, inducing movement. And some ancient dispersals were no doubt entirely accidental and without motives, for example, where a group by chance tracked game into an entirely new region, or where a boat with people on board was carried to an unintended destination by unfavorable tides or winds.

Genetic data and physical proximity suggest that northeast Africa provided the immediate source area for the dispersal from Africa. There is evidence from Lake Naivasha in Kenya that East Africa was relatively well watered about 60,000 years ago, and data from both Antarctic and Indian Ocean cores suggest that the climate was relatively warm at that time, perhaps providing the right environment for population growth and another acceleration in innovation. There are many Middle Stone Age sites in Ethiopia, Kenya, and Tanzania that demonstrate human occupation around this time, but their study and dating are still largely in progress, and so it is difficult to relate them precisely to the time of the modern human dispersal from Africa. An example is the rich site of Magubike rock shelter in Tanzania, being excavated by Pamela Willoughby and her colleagues, where I am involved in the study of fossil human teeth. But there are published findings from one important site: a rock shelter near Lake Naivasha, Enkapune ya Muto (Twilight Cave). This lies close to sources of obsidian (a volcanic glass highly prized for making stone tools) at an elevation of 2,400 meters, with a rich record of Middle Stone Age and succeeding Later Stone Age occupation. The earliest levels of the latter industry show many innovative features such as specialized tools, red ocher use, and ostrich egg shell beads, dated to more than 46,000 years old.

In chapter 4 I discussed routes out of Africa and possible connections between North Africa, the Middle East, and Europe between 40,000 and 50,000 years ago. The most obvious pathway out of Africa would have been up the Nile Valley, through Sinai, and thence into the Levant (the region adjoining the eastern Mediterranean coast). Suggestions that another route could have existed at the other end of the Mediterranean—by boat across the Strait of Gibraltar—are appealing when one considers that the Strait was narrower during the last glacial, and there may even have been intervening islands at times. But good archaeological or fossil human evidence of an ancient connection is still elusive, with no sign of true Neanderthals in North Africa, nor of moderns at an early date in southern Iberia. On the contrary, the region seems to have been one of the last outposts of the Neanderthals. It is possible that populations did cross from time to time but could not gain a foothold, but the fact that Mediterranean islands like Malta, the Balearics, Sardinia, and Cyprus do not seem to have been impacted by humans until much later also speaks against such mobility by early moderns and Neanderthals (although there are recent claims that African-looking handaxes were discovered on Crete).

But what about pathways farther east? We saw that there is evidence of the use of coastal resources in South Africa during the Middle Stone Age between 60,000 and 160,000 years ago, at sites like Pinnacle Point, Blombos, and Klasies River Mouth Caves, and the pattern is matched at sites scattered around the North and East African coasts, with a particularly interesting example at Abdur, on the Eritrean Red Sea, dated to the high sea level of the last interglacial, about 125,000 years ago. In the 1960s the American geographer Carl Sauer proposed that “the dispersal of early man took place most readily by following along the seashore. The coasts ahead presented familiar foods and habitats … Coastwise there was scarcely a barrier to the spread … through tropical and subtropical latitudes … The Indian Ocean, likeliest sea of earliest human occupation, exhibits to a large extent … an inviting articulation of shoreline, from Africa to the Sunda Islands [of southeast Asia].”

Some thirty years later the zoologist Jonathan Kingdon suggested that Middle Stone Age people left Africa through the Middle East and reached southeast Asia by 90,000 years ago, where they adapted to coastal living, including the development of a boat- or raft-building capability. This enabled them both to return westward to Africa and to move southward to Australasia. The anthropologists Marta Lahr and Robert Foley proposed in their Multiple Dispersals model that a more direct route from Africa to Arabia and farther east could have been taken before 50,000 years ago, perhaps using the coasts, and exiting by boat across the Bab-el-Mandeb strait at the southern end of the Red Sea. Geneticists such as Spencer Wells and Stephen Oppenheimer have also favored this route, arguing that only a few hundred people may have made the fateful crossing into Arabia, to found the populations of the rest of the world.

Personally I have never seen the necessity of invoking this complication in our African exodus, since if people were on the western coast of the Red Sea they would only have needed to travel north, around Sinai, and then south again down the eastern coast of the Red Sea. Continuing along the narrow ribbon of shoreline, to which they were already adapted, they could have progressed within a few millennia all the way to Indonesia at times of low sea level, and could have been spared the level of habitat disruption faced by inland populations during the rapid climatic fluctuations of the late Pleistocene. Population increase or depletion of resources would have driven the dispersal, and the development of watercraft could have followed from the need to traverse natural barriers such as dense mangrove forests or river estuaries, or to extend coastal foraging opportunities. These coastal populations could then have penetrated up river valleys into the interior, and by the end of their journey through southeast Asia, they would have been ready for the (probably fortuitous) first steps toward New Guinea and Australia (then joined as one enlarged continent).

The region of Arabia probably did form an important transit route for Out of Africa pioneers, but until recently it was largely terra incognita in terms of hard data, leading to much theorizing. Recently, however, several international teams have been trying to fill this void through fieldwork in the area. Archaeologists like Jeffrey Rose and Michael Petraglia have argued that it was not just a place that people passed through but an important locus for early humans in its own right. When environments were hyperarid in western Asia, it provided refuge with its ephemeral rivers and lakes, and its coastal margins, as these were exposed by falls in sea level. Despite the confounding lack of diagnostic fossil evidence, research by Simon Armitage and his colleagues at Jebel Faya (United Arab Emirates) provided important clues that early modern humans might even have dispersed from Africa, across Arabia as far as the Straits of Hormuz, by 120,000 years ago. This research augments the controversial idea that such modern populations could have migrated even farther across southern Asia, despite the conflicting genetic data that movements only occurred after 60,000 years. However, the fact that the artifacts at Jebel Faya look “African” and do not resemble those associated with the contemporaneous Skhul and Qafzeh people in the Levant signals yet more complexity in the exodus of modern humans from Africa. Could there have been separate early dispersals, one from East Africa into Arabia and another from North Africa into the Levant? And what was the fate of these different populations 100,000 years ago? Did they die out, did they survive in small pockets, did they perhaps interbreed with neighboring archaic peoples, or could they indeed have spread farther eastward?