The Rational Optimist (8 page)

What is true of extant hunter-gatherers was equally true of extinct ways of life, as far as can be ascertained. Cree Indian women hunted hares; men hunted moose. Chumash women in California gathered shellfish; men harpooned sea lions. Yahgan Indians (in Tierra del Fuego) hunted otters and sea lions; women fished. In the Mersey estuary near Liverpool are preserved dozens of 8,000-year-old footprints: the women and children appear to have been collecting razor clams and shrimps; the men’s prints are moving fast and paralleling those of red and roe deer.

An evolutionary bargain seems to have been struck: in exchange for sexual exclusivity, the man brings meat and protects the fire from thieves and bullies; in exchange for help rearing the children, the woman brings veg and does much of the cooking. This may explain why human beings are the only great apes with long pair bonds.

Just to be clear, this argument has nothing to do with the notion that ‘a woman’s place is in the home’ while men go out to work. Women work hard in hunter-gatherer societies, often harder than men. Neither gathering nor hunting is especially good evolutionary preparation for sitting at a desk answering the telephone. Anthropologists used to argue that the sexual division of labour came about because of the long, helpless childhood of human beings. Because women could not abandon their babies, they could not hunt game, so they stayed near the home and gathered and cooked food of the kind that was compatible with caring for children. With a baby strapped to your back and a toddler giggling at your feet, it is undoubtedly easier to gather fruit and dig roots than it is to ambush an antelope. The anthropologists have been revising the view that the division of labour by sex is all about childcare constraints, though. They have found that even when hunter-gatherer women do not face a hard choice between child care and hunting, they still seek out different kinds of food from their menfolk. In the Alyawarre aborigines of Australia, while young women care for children, older women go out looking for goanna lizards, not for the kangaroos and emus that their menfolk hunt. A sexual division of labour would exist even without childcare constraints.

When did this specialisation begin? There is a neat economic explanation for the sexual division of labour in hunter-gatherers. In terms of nutrition, women generally collect dependable, staple carbohydrates whereas men fetch precious protein. Combine the two – predictable calories from women and occasional protein from men – and you get the best of both worlds. At the cost of some extra work, women get to eat some good protein without having to chase it; men get to know where the next meal is coming from if they fail to kill a deer. That very fact makes it easier for them to spend more time chasing deer and so makes it more likely they will catch one. Everybody gains – gains from trade. It is as if the species now has two brains and two stores of knowledge instead of one – a brain that learns about hunting and a brain that learns about gathering.

Neat, as I say. There are untidy complications to the story, including that men seem to strive to catch big game to feed the whole band – in exchange for both status and the occasional seduction – while women feed the family. This can lead to men being economically less productive than they might be. Hadza men spend weeks trying to catch a huge eland antelope when they could be snaring a spring-hare each day instead; men on the island of Mer in the Torres Strait stand with spears at the fringe of the reef hoping to harpoon giant trevally while their women gather twice as much food by collecting shellfish. Yet even allowing for such conspicuous generosity or social parasitism – depends on how you view it – the economic benefits of food sharing and specialised sex roles are real. They are also unique to human beings. There are a few birds in which the sexes have slightly different feeding habits – in the extinct Huia of New Zealand male and female even had different beak shapes – but collecting different foods and sharing them is something no other species does. It is a habit that put an end to self-sufficiency long ago and that got our ancestors into the habit of exchange.

When was the sexual division of labour invented? The cooking theory points to half a million years ago or much more, but two archaeologists argue otherwise. Steven Kuhn and Mary Stiner think that modern, African-origin
Homo sapiens
had a sexual division of labour and Neanderthals did not, and that this was the former’s crucial ecological advantage over the latter when they came head-to-head in Eurasia 40,000 years ago. In advancing this notion they are contradicting a long-held tenet of their science, first advocated by Glyn Isaac in 1978 – that different sex roles started with food sharing millions of years ago. They point out that there is just no sign of the kind of food normally brought by gatherer women in Neanderthal debris, nor of the elaborate clothing and shelters that Inuit women make while their men are hunting. There are occasional shellfish, tortoises, eggshells and the like – foods easily picked up while hunting – but no grindstones and no sign of nuts and roots. This is not to deny that Neanderthals cooperated, and cooked. But it is to challenge the notion that the sexes had different foraging strategies and swapped the results. Either the Neanderthal women sat around doing nothing, or, since they were as butch as most modern men, they went out hunting with the men. That seems more likely.

This is a startling shift of view. Instead of talking about ‘hunter-gathering’ as the natural state of humanity effectively since forever, as they are apt to do, scientists must begin to consider the possibility that it is a comparatively recent phase, an innovation of the last 200,000 years or so. Is the sexual division of labour a possible explanation of what made a small race of Africans so much better at surviving in a time of megadroughts and volatile climate change than all other hominids on the planet?

Perhaps. Remember how few are the remains from Neanderthal sites. But at least the burden of proof has shifted a bit. Even if the habit is more ancient, it may have been the predisposing factor that then conditioned the African race to the whole notion of specialisation and exchange. Having trained themselves to specialise and exchange between the sexes, having got into the habit of exchanging labour with others, the thoroughly modern Africans had then begun to extend the idea a little bit further and tentatively try a new and still more portentous trick, of specialising within the band and then between bands. This latter step was very hard to take, because of the homicidal relationships between tribes. Famously, no other species of ape can encounter strangers without trying to kill them, and the instinct still lurks in the human breast. But by 82,000 years ago, human beings had overcome this problem sufficiently to be able to pass
Nassarius
shells hand to hand 125 miles inland. Barter had begun.

Beachcombing east

Barter was the trick that changed the world. To paraphrase H.G. Wells, ‘We had struck our camp forever, and were out upon the roads.’ Having conquered much of Africa by about 80,000 years ago, the modern people did not stop there. Genes tell an almost incredible story. The pattern of variation in the DNA of both mitochondrial and Y chromosomes in all people of non-African origin attests that some time around 65,000 years ago, or not much later, a group of people, numbering just a few hundred in all, left Africa. They probably crossed the narrow southern end of the Red Sea, a channel much narrower then than it is now. They then spread along the south coast of Arabia, hopping over a largely dry Persian Gulf, skirting round India and a then-connected Sri Lanka, moving gradually down through Burma, Malaya and along the coast of a landmass called Sunda in which most of the Indonesian islands were then embedded, until they came to a strait somewhere near Bali. But they did not stop there either. They paddled across at least eight straits, the largest at least forty miles wide, presumably on canoes or rafts, working their way through an archipelago to land, probably around 45,000 years ago, on the continent of Sahul, in which Australia and New Guinea were conjoined.

This great movement from Africa to Australia was not a migration, but an expansion. As bands of people feasted on the coconuts, clams, turtles, fish and birds on one part of the coast and grew fat and numerous, so they would send out pioneers (or exile troublemakers?) to the east in search of new camp sites. Sometimes these emigrants would have to leapfrog others already in possession of the coast by trekking inland or taking to canoes.

Along the way they left tribes of hunter-gatherer descendants, a few of whom survive to this day genetically unmixed with other races. On the Malay Peninsula, forest hunter-gatherers called the Orang Asli (‘original people’) look ‘negrito’ in appearance and prove to have mitochondrial genes that branched off from the African tree about 60,000 years ago. In New Guinea and Australia, too, the genetics tell an unambiguous story of almost complete isolation since the first migration. Most remarkable of all, the native people of the Andaman islands, black-skinned, curly-haired and speaking a language unrelated to any other, have Y-chromosome and mitochondrial genes that diverged from the common ancestor with the rest of humankind 65,000 years ago. At least this is true of the Jarawa tribe on Great Andaman. The North Sentinelese, on the nearby island of North Sentinel, have not volunteered to give blood – at least not their own. As the only hunter-gatherers who still resist ‘contact’, these fine-looking people – strong, slim, fit and stark naked except for a small plant-fibre belt round the waist – usually greet visitors with showers of arrows. Good luck to them.

To reach the Andaman islands (then closer to the Burmese coast, but still out of sight) and Sahul, however, the migrants of 65,000 years ago must have been proficient canoeists. It was in the early 1990s that the African-born zoologist Jonathan Kingdon first suggested that the black skin of many Africans, Australians, Melanesians and ‘negrito’ Asians hinted at a maritime past. For a hunter-gatherer on the African savannah, a very black skin is not needed, as the relatively pale Khoisan and pygmies prove. But out on an exposed reef or beach, or in a fishing canoe, maximum sunscreen is called for. Kingdon believed that the ‘Banda strandlopers’, as he called them, had returned to conquer Africa from Asia, rather than the other way round, but he was ahead of the genetic evidence in coining the idea of an essentially maritime Palaeolithic race.

This remarkable expansion of the human race along the shore of Asia, now known as the ‘beachcomber express’, has left few archaeological traces, but that is because the then coastline is now 200 feet under water. It was a cool, dry time with vast ice sheets in high latitudes and big glaciers on mountain ranges. The interior of many of the continents was inhospitably dry, windy and cold. But the low-lying coasts were dotted with oases of freshwater springs. The low sea level not only exposed more springs, but increased the relative pressure on underground aquifers to discharge near the coast. All along the coast of Asia, the beachcombers would have found fresh water bubbling up and flowing into streams that meandered down to the ocean. The coast is also rich in food if you have the ingenuity to find it, even on desert shores. It made sense to stick to the beach.

The evidence of DNA attests that some of these beachcombers, on reaching India and apparently not before, must have eventually moved inland, because by 40,000 years ago ‘modern’ people were pressing west into Europe and east into what is now China. Abandoning the crowded coast, they resumed their old African ways of hunting game and gathering fruits and roots, becoming gradually more dependent on hunting once more as they inched north into the steppes grazed by herds of mammoths, horses and rhinoceroses. Soon they came across their distant cousins, the descendants of
Homo erectus
, with whom they last shared an ancestor half a million years before. They got close enough to acquire the latter’s lice to add to their own, so louse genes suggest, and conceivably even close enough to acquire a smattering of their cousins’ genes by interbreeding. But inexorably they rolled back the territory of these Eurasian erectus hominids till the last survivor, of the European cold-adapted sort known as Neanderthal, died with his back to the Strait of Gibraltar about 28,000 years ago. Another 15,000 years saw some of them spilling into the Americas from north-east Asia.

They were very good at wiping out not only their distant cousins, but also much of their prey, something previous hominid species had not managed. The earliest of the great cave painters, working at Chauvet in southern France 32,000 years ago, was almost obsessed with rhinoceroses. A more recent artist, working at Lascaux 15,000 years later, depicted mostly bisons, bulls and horses – rhinoceroses were rare or extinct in Europe by then. At first, modern human beings around the Mediterranean relied mostly on large mammals for meat. They ate small game only if it was slow-moving – tortoises and limpets were popular. Then, gradually and inexorably, starting in the Middle East, they switched their attention to smaller animals, and especially to fast-breeding species, such as rabbits, hares, partridges and smaller gazelles. They gradually stopped eating tortoises. The archaeological record tells this same story at sites in Israel, Turkey and Italy.

The reason for this shift, say Mary Stiner and Steven Kuhn, was that human population densities were growing too high for the slower-reproducing prey such as tortoises, horses and elephants. Only the fast-breeding rabbits, hares and partridges, and for a while gazelles and deer, could cope with such hunting pressure. This trend accelerated about 15,000 years ago as large game and tortoises disappeared from the Mediterranean diet altogether – driven to the brink of extinction by human predation. (A modern parallel: in the Mojave Desert of California, ravens occasionally kill tortoises for food. But only when landfills provided the ravens with ample alternative food and boosted – subsidised – their numbers did the tortoise numbers start to collapse from raven predation. So modern people, subsidised by hare meat, could extinguish mammoths.)