The Rational Optimist: How Prosperity Evolves

In other words, cooking encourages specialisation by sex. The first and deepest division of labour is the sexual one. It is an iron rule documented in virtually all foraging people that ‘men hunt, women and children gather (#litres_trial_promo)’. The two sexes move ‘through the same habitat, making strikingly different decisions about how to obtain resources within that habitat (#litres_trial_promo), and often returning to a central location with the results of their labour.’ So, for example, while Hiwi women in Venezuela travel by foot to dig roots, pound palm starch, pick legumes and collect honey, their menfolk go hunting, fishing or collecting oranges by canoe; while Ache men in Paraguay hunt pigs, deer and armadillos for up to seven hours a day, the women follow them collecting fruit, digging for roots, gathering insects or pounding starch – and sometimes catching armadillos, too; while Hadza women in Tanzania collect tubers, fruit and nuts, men hunt antelope; while Greenland Inuit men hunt seals, women make stews, tools and clothing from the animals. And so on, through example after example. Even the apparent exceptions to the rule, where women do hunt, are instructive, because there is still a division of labour. Agta women in the Philippines hunt with dogs; men hunt with bows. Martu women in western Australia hunt goanna lizards (#litres_trial_promo); men hunt bustards and kangaroos. As one anthropologist put it after living with the Khoisan, ‘Women demand meat as their social right, and they get it – otherwise they leave their husbands, marry elsewhere or make love to other men (#litres_trial_promo).’

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 (#litres_trial_promo) 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 (#litres_trial_promo), 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. (#litres_trial_promo)

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 (#litres_trial_promo) 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 (#litres_trial_promo) – 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 (#litres_trial_promo) when they could be snaring a spring-hare each day instead; men on the island of Mer in the Torres Strait (#litres_trial_promo) 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 (#litres_trial_promo), 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 (#litres_trial_promo) – 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 (#litres_trial_promo), ‘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 (#litres_trial_promo), 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 (#litres_trial_promo). 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 (#litres_trial_promo) 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 (#litres_trial_promo) 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 (#litres_trial_promo), and conceivably even close enough to acquire a smattering of their cousins (#litres_trial_promo)’ 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 (#litres_trial_promo). (A modern parallel: in the Mojave Desert of California, ravens occasionally kill tortoises for food (#litres_trial_promo). 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.)

It is rare for a predator to wipe out its prey altogether. In times of prey scarcity, erectus hominids, like other predators, had simply suffered local depopulation; that in turn would have saved the prey from extinction and the hominid numbers could recover in time. But these new people could innovate their way out of trouble; they could shift their niche, so they continued to thrive even as they extinguished their old prey. The last mammoth to be eaten on the Asian plain was probably thought a rare delicacy, a nice change from hare and gazelle stew. As they adjusted their tactics to catch smaller and faster prey, so the moderns developed better weapons, which in turn enabled them to survive at high densities, though at the expense of extinguishing more of the larger and slower-breeding prey. This pattern of shifting from big prey to small as the former were wiped out was characteristic of the new ex-Africans wherever they went. In Australia, almost all larger animal species, from diprotodons to giant kangaroos, became extinct soon after human beings arrived. In the Americas, human arrival coincided with a sudden extinction of the largest, slowest-breeding beasts. Much later in Madagascar and New Zealand mass extinctions of large animals also followed with human colonisation. (Incidentally, given the obsession of ‘show-off’ male hunters with catching the largest beasts with which to buy prestige in the tribe, it is worth reflecting that these mass extinctions owe something to sexual selection.)

Shall we trade?

Meanwhile, the stream of new technologies gathered pace. From around 45,000 years ago, the people of western Eurasia had progressively revolutionised their toolkit. They struck slim, sharp blades from cylindrical rock ‘cores’ – a trick that produces ten times as much cutting edge as the old way of working, but is far harder to pull off. By 34,000 years ago they were making bone points for spears, and by 26,000 they were making needles. Bone spear throwers, or atlatls – which greatly increase the velocity of javelins – appear by 18,000 years ago. Bows and arrows came soon afterwards. ‘Microburin’ borers were used for drilling the holes in needles and beads. Of course, stone tools would have been only a tiny tip of a technological iceberg, dominated by wood, which has long since rotted away. Antler, ivory and bone were just as important. String, made from plant fibres or leather, was almost certainly in use by then to catch fish and rabbits in nets or snares, and to make bags for carrying things in.

Nor was this virtuosity confined to practicalities. As well as bone and ivory, shells, fossil coral, steatite, jet, lignite, hematite, and pyrite were used to make ornaments and objects (#litres_trial_promo). A flute made from the bone of a vulture (#litres_trial_promo) dates from 35,000 years ago at Hohle Fels and a tiny horse, carved from mammoth ivory and worn smooth by being used as a pendant, dates from 32,000 years ago at Vogelherd – both in Germany. By the time of Sungir, an open-air settlement from 28,000 years ago at a spot near the city of Vladimir, north-east of Moscow, people were being buried in clothes decorated with thousands of laboriously carved ivory beads, and even little wheel-shaped bone ornaments had appeared. At Mezherich, in what is now Ukraine, 18,000 years ago, jewellery made of shells from the Black Sea and amber from the Baltic (#litres_trial_promo) implied trade over hundreds of miles.

This is in striking contrast to the Neanderthals, whose stone tools were virtually always made from raw material available within an hour (#litres_trial_promo)’s walk of where the tool was used. To me this is a vital clue to why the Neanderthals were still making hand axes, while their African-origin competitors were making ever more types of tool. Without trade, innovation just does not happen. Exchange is to technology as sex is to evolution. It stimulates novelty. The remarkable thing about the moderns of west Asia is not so much the diversity of artefacts as the continual innovation. There is more invention between 80,000 and 20,000 years ago than there had been in the previous million. By today’s standards, it was very slow, but by the standards of Homo erectus it was lightning-fast. And the next ten millennia would see still more innovations: fish hooks, all sorts of implements, domesticated wolves, wheat, figs, sheep, money.

If you are not self-sufficient, but are working for other people, too, then it pays you to spend some time and effort to improve your technology and it pays you to specialise. Suppose, for example, that Adam lives in a grassy steppe where there are herds of reindeer in winter, but some days’ walk away is a coast, where there are fish in summer. He could spend winter hunting, then migrate to the coast to go fishing. But that way he would not only waste time travelling, and probably run a huge risk crossing the territory of another tribe. He would also have to get good at two quite different things.

If, instead, Adam sticks to hunting and then gives some dried meat and reindeer antlers – ideal for fashioning hooks from – to Oz, a coastal fisherman, in exchange for fish, he has achieved the goal of varying his diet in a less tiring or dangerous way. He has also bought an insurance policy. And Oz would be better off, because he could now catch (and spare) more fish. Next Adam realises that instead of giving Oz raw antlers, he can give him pieces of antler already fashioned into hooks. These are easier to transport and fetch a better price in fish. He got the idea when he once went to the trading point and noticed others selling antlers that had already been cut up into easy segments. One day, Oz asks him to make barbed hooks. And Adam suggests that Oz dries or smokes his fish so it lasts longer. Soon Oz brings shells, too, which Adam buys to make jewellery for a young woman he fancies. After a while, depressed by the low price fetched by hooks of even high quality, Adam hits on the idea of tanning some extra hides and bringing those to the trading point, too. Now he finds he is better at making hides than hooks, so he specialises in hides, giving his antlers to somebody from his own tribe in exchange for his hides. And so on, and on and on.

Fanciful, maybe. And no doubt wrong in all sorts of details. But the point is how easy it is to envisage both opportunities for trade among hunter-gatherers – meat for plants, fish for leather, wood for stone, antler for shells – and how easy it is for Stone Age people to discover mutual gains from trade and then to enhance that effect by further specialising and further dividing labour. The extraordinary thing about exchange is that it breeds: the more of it you do, the more of it you can do. And it calls forth innovation.

Which only raises another question: why did economic progress not accelerate towards an industrial revolution there and then? Why was progress so agonisingly slow for so many millennia? The answer, I suspect, lies in the fissile nature of human culture. Human beings have a deep capacity for isolationism, for fragmenting into groups that diverge from each other. In New Guinea, for instance, there are more than 800 languages, some spoken in areas just a few miles across yet as unintelligible to those on either side as French and English. There are still 7,000 languages spoken on earth and the people who speak each one are remarkably resistant to borrowing words, traditions, rituals or tastes from their neighbours. ‘Whereas vertical transmission of cultural traits goes largely unnoticed, horizontal transmission is far more likely to be regarded with suspicion or even indignation,’ say the evolutionary biologists Mark Pagel and Ruth Mace (#litres_trial_promo). ‘Cultures, it seems, like to shoot messengers.’ People do their utmost to cut themselves off from the free flow of ideas, technologies and habits, limiting the impact of specialisation and exchange.

Ricardo’s magic trick

Divisions of labour beyond the pair bond had probably been invented in the Upper Palaeolithic. Commenting on the ten thousand mammoth-ivory beads with which the clothing of two 28,000-year-old child corpses at Sungir in Russia were decorated, the anthropologist Ian Tattersall remarks (#litres_trial_promo): ‘It’s hardly probable that these young people had made their richly adorned vestments themselves. It’s much more likely that the sheer diversity of material production in their society was the result of the specialisation of individuals in different activities.’ The carvers of mammoth beads at Sungir, the painter of rhinoceroses at Chauvet, the striker of blades from rock cores, the maker of rabbit nets – perhaps these were all specialists, exchanging their labour for that of others. Perhaps there had been different roles within each band of human beings ever since the first emergence of modern people over 100,000 years ago.

It is such a human thing to do, and so obvious an explanation of the thing that needs explaining: the capacity for innovation. Specialisation would lead to expertise, and expertise would lead to improvement. Specialisation would also give the specialist an excuse for investing time in developing a laborious new technique. If you have a single fishing harpoon to make, there’s no sense in building a clever tool for making harpoons first, but if you have to make harpoons for five fishermen, then maybe there is sense and time-saving in first making the harpoon-making tool.

Specialisation would therefore create and increase the opportunities for gains from trade. The more Oz goes fishing, the better he gets at it, so the less time it takes him to catch each fish. The more hooks Adam the reindeer hunter makes, the better he gets at it, so the less time he takes to make each one. So it pays Oz to spend his day fishing and buy his hooks off Adam by giving him some fish. And it pays Adam to spend his day making hooks and get his fish delivered by Oz.

And, wonderfully, this is true even if Oz is better at hook-making than Adam. Suppose Adam is a clumsy fool, who breaks half his hooks, but he is an even clumsier fisherman who cannot throw a line to save his life. Oz, meanwhile, is one of those irritating paragons who can whittle a bone hook with little trouble and always catches lots of fish. Yet it still pays Oz to get his hooks made for him by clumsy Adam. Why? Because with practise Adam has at least become better at making hooks than he is at fishing. It takes him three hours to make a hook, but four hours to catch a fish. Oz takes only an hour to catch a fish, but good as he is he still needs two hours to make a hook. So if each is self-sufficient, then Oz works for three hours (two to make the hook and one to catch the fish), while Adam works for seven hours (three to make the hook and four to catch a fish). If Oz catches two fish and swaps one for a hook from Adam, he only has to work two hours. If Adam makes two hooks and uses one to buy a fish from Oz, he only works for six hours. Both are better off than when they were self-sufficient. Both have gained an hour of leisure time.

I have done nothing here but retell, in Stone Age terms, the notion of comparative advantage as defined by the stockbroker David Ricardo in 1817 (#litres_trial_promo). He used the example of England trading cloth for Portuguese wine, but the argument is the same:

England may be so circumstanced, that to produce the cloth may require the labour of 100 men for one year; and if she attempted to make the wine, it might require the labour of 120 men for the same time. England would therefore find it in her interest to import wine, and to purchase it by the exportation of cloth. To produce the wine in Portugal, might require only the labour of 80 men for one year, and to produce the cloth in the same country, might require the labour of 90 men for the same time. It would therefore be advantageous for her to export wine in exchange for cloth. This exchange might even take place, notwithstanding that the commodity imported by Portugal could be produced there with less labour than in England.

Ricardo’s law has been called the only proposition in the whole of the social sciences that is both true and surprising. It is such an elegant idea that it is hard to believe that Palaeolithic people took so long to stumble upon it (or economists to define it) (#litres_trial_promo); hard to understand why other species do not make use of it, too. It is rather baffling that we appear to be the only species that routinely exploits it. Of course, that is not quite right. Evolution has discovered Ricardo’s law and applied it to symbioses, such as the collaboration between alga and fungus that is a lichen plant or the collaboration between a cow and a bacterium in a rumen. Within species, too, there are clear gains from trade between cells of a body, polyps of a coral colony, ants of an ant colony, or mole-rats of a mole-rat colony. The great success of ants and termites – between them they may comprise one-third of all the animal biomass of land animals – is undoubtedly down to their division of labour. Insect social life is built not on increases in the complexity of individual behaviour, ‘but instead on specialization among individuals’. In the leafcutter ants of the Amazon rainforest, colonies may number millions, and workers grow into one of four distinct castes: minors, medias, majors and supermajor. In one species a supermajor (or soldier) may weigh the same as 500 minors.

But the big difference is that in every other species than human beings, the colonies consist of close relatives – even a city of a million ants is really just a huge family. Yet reproduction is the one task that people never delegate to a specialist, let alone a queen. What gave people the chance to exploit gains from trade, without waiting for Mother Nature’s tedious evolutionary crawl, was technology. Equipped with the right tool, a human being can become a soldier or a worker (maybe not a queen), and he can switch between the roles. The more you do something, the better you get at it. A band of hunter-gatherers in west Eurasia, 15,000 years ago, dividing labour not just by gender but by individual as well, would have been formidably more efficient than an undifferentiated band. Imagine, say, 100 people in the band. Some of them make tools, others make clothes, others hunt, others gather. One tiresome bloke insists on prancing around in a deer skull chanting spells and prayers, adding little to the general well-being, but then maybe he is in charge of the lunar calendar so he can tell people when the tides will be lowest for limpet-picking expeditions.

True, there is not much specialisation in modern hunter-gatherers. In the Kalahari or the Australian desert, apart from the gathering women, the hunting men and maybe the shaman, there are not too many distinct occupations in each band. But these are the simple societies left in the harsh habitats. In the relatively fertile lands of west Eurasia after 40,000 years ago, when bands of people were larger and lines of work were diverse, specialisation had probably grown up within each band. The Chauvet rhino painter was so good at his job (and yes, archaeologists think it was mainly one artist) that he must surely have had plenty of time off hunting duties to practise. The Sungir bead maker must have been working for a wage of some kind, because he cannot surely have had time to hunt for himself. Even Charles Darwin reckoned (#litres_trial_promo) that ‘primeval man practised a division of labour; each man did not manufacture his own tools or rude pottery, but certain individuals appear to have devoted themselves to such work, no doubt receiving in exchange the produce of the chase.’

Innovation networks

According to the anthropologist Joe Henrich (#litres_trial_promo), human beings learn skills from each other by copying prestigious individuals, and they innovate by making mistakes that are very occasionally improvements – that is how culture evolves. The bigger the connected population, the more skilled the teacher, and the bigger the probability of a productive mistake. Conversely, the smaller the connected population, the greater the steady deterioration of the skill as it was passed on. Because they depended on wild resources, hunter-gatherers could rarely live in bands larger than a few hundred and could never achieve modern population densities. This had an important consequence. It meant that there was a limit to what they could invent. A band of a hundred people cannot sustain more than a certain number of tools, for the simple reason that both the production and the consumption of tools require a minimum size of market. People will only learn a limited set of skills and if there are not enough experts to learn one rare skill from, they will lose that skill. A good idea, manifest in bone, stone or string, needs to be kept alive by numbers. Progress can easily falter and turn into regress.

Where modern hunter-gatherers have been deprived of access to a large population of trading partners – in sparsely populated Australia, especially Tasmania, and on the Andaman islands, for example – their technological virtuosity was stunted and barely progressed beyond those of Neanderthals. There was nothing special about the brains of the moderns; it was their trade networks that made the difference – their collective brains.

The most striking case of technological regress is Tasmania (#litres_trial_promo). Isolated on an island at the end of the world, a population of less than 5,000 hunter-gatherers divided into nine tribes did not just stagnate, or fail to progress. They fell steadily and gradually back into a simpler toolkit and lifestyle, purely because they lacked the numbers to sustain their existing technology. Human beings reached Tasmania at least 35,000 years ago while it was still connected to Australia. It remained connected – on and off – until about 10,000 years ago, when the rising seas filled the Bass Strait. Thereafter the Tasmanians were isolated. By the time Europeans first encountered Tasmanian natives, they found them not only to lack many of the skills and tools of their mainland cousins, but to lack many technologies that their own ancestors had once possessed. They had no bone tools of any kind, such as needles and awls, no cold-weather clothing, no fish hooks, no hafted tools, no barbed spears, no fish traps, no spear throwers, no boomerangs. A few of these had been invented on the mainland after the Tasmanians had been isolated from it – the boomerang, for instance – but most had been made and used by the very first Tasmanians. Steadily and inexorably, so the archaeological history tells, these tools and tricks were abandoned. Bone tools, for example, grew simpler and simpler until they were dropped altogether about 3,800 years ago. Without bone tools it became impossible to sew skins into clothes, so even in the bitter winter, the Tasmanians went nearly naked but for seal-fat grease smeared on their skin and wallaby pelts over their shoulders. The first Tasmanians caught and ate plenty of fish, but by the time of Western contact they not only ate no fish and had eaten none for 3,000 years, but they were disgusted to be offered it (though they happily ate shellfish).

The story is not quite that simple, because the Tasmanians did invent a few new things during their isolation. Around 4,000 years ago they came up with a horribly unreliable form of canoe-raft, made of bundles of rushes and either paddled by men or pushed by swimming women (!), which enabled them to reach offshore islets to harvest birds and seals. The raft would become waterlogged and disintegrate or sink after a few hours, so it was no good for re-establishing contact with the mainland. As far as innovation goes, it was so unsatisfactory that it almost counts as an exception to prove the rule. The women also learnt to dive up to twelve feet below the water to prise clams off the rocks with wooden wedges and to grab lobsters. This was dangerous and exhausting work, which they were very skilled at: the men did not take part. So it was not that there was no innovation; it was that regress overwhelmed progress (#litres_trial_promo).

The archaeologist who first described the Tasmanian regress, Rhys Jones, called it a case of the ‘slow strangulation of the mind’, which perhaps understandably enraged some of his academic colleagues. There was nothing wrong with individual Tasmanian brains; there was something wrong with their collective brains. Isolation – self-sufficiency – caused the shrivelling of their technology. Earlier I wrote that division of labour was made possible by technology. But it is more interesting than that. Technology was made possible by division of labour: market exchange calls forth innovation.

Now, at last, it becomes clear why the erectus hominids saw such slow technological progress. They, and their descendants the Neanderthals, lived without trade (recall how Neanderthal stone tools were sourced within an hour’s walk of their use). So in effect each erectus hominid tribe occupied a virtual Tasmania, cut off from the collective brain of the wider population. Tasmania is about the size of the Irish Republic. By the time Abel Tasman pitched up in 1642 it held probably about 4,000 hunter-gatherers divided into nine tribes, and they lived mainly off seals, seabirds and wallabies, which they killed with wooden clubs and spears. That means that there were only a few hundred young adults on the entire island who were learning new skills at any one time. If, as seems to be the case everywhere, culture works by faithful imitation with a bias towards imitating prestigious individuals (in other words, copy the expert, not the parent or the person closest to hand), then all it would take for certain skills to be lost would be a handful of unlucky accidents in which the most prestigious individual had forgotten or mislearned a crucial step or even gone to his grave without teaching an apprentice. Suppose, for example, that an abundance of seabirds led one group to eschew fishing for a number of years until the last maker of fishing tackle had died. Or that the best barbed-spear maker on the island fell off a cliff one day leaving no apprentice. His barbs went on being used for some years, but once they had all broken, suddenly there was nobody who could make them. Acquiring a skill costs a lot of time and effort; nobody could afford to learn barb-making from scratch. People concentrated on learning the skills that they could watch first-hand.

Bit by bit, Tasmanian technology simplified. The most difficult tools and complex skills were lost first, because they were the hardest to master without a master to learn from. Tools are in effect a measure of the extent of the division of labour and, as Adam Smith argued, the division of labour is limited by the extent of the market. The Tasmanian market was too small to sustain many specialised skills (#litres_trial_promo). Imagine if 4,000 people from your home town were plonked on an island and left in total isolation for ten millennia. How many skills and tools do you think they could preserve? Wireless telephony? Double-entry book-keeping? Suppose one of the people in your town was an accountant. He could teach double-entry book-keeping to a youth, but would the youth or the youth’s youth pass it on – for ever?

On other Australian islands much the same thing happened as on Tasmania. On Kangaroo Island and Flinders Island, human occupation petered out, probably by extinction, a few thousand years after isolation (#litres_trial_promo). Flinders is a fertile island that should be a paradise. But the hundred or so people it could support were far too small a human population to sustain the technology of hunter-gathering. The Tiwi people, isolated on two islands north of Darwin for 5,500 years, also reversed the ratchet of accumulating skills and slipped back to a simpler tool set. The Torres islanders lost the art of canoe making, causing the anthropologist W.H.R. Rivers to puzzle (#litres_trial_promo) over the ‘disappearance of the useful arts’. It seems the hunter-gathering lifestyle was doomed if too isolated. The Australian mainland, by contrast, experienced steady technological progress. Where Tasmanian spears merely had fire-hardened wood points, on the mainland spears acquired detachable tips, stone barbs and ‘woomera’ spear throwers. It is no coincidence that the mainland had long-range trade, so that inventions and luxuries could be sourced from distant parts of the land. Shell beads had been moving long distances across Australia since at least 30,000 years ago. (#litres_trial_promo) Pearl and baler shell pendants from the north coast moved through at least eight tribal areas to reach the far south more than a thousand miles from where they had been harvested, growing in sacredness as they went. ‘Pitchera’ – a tobacco-like plant – moved west from Queensland. The best stone axes travelled up to 500 miles from where they were mined. (#litres_trial_promo)

In contrast to Tasmania, Tierra del Fuego (#litres_trial_promo) – an island not much bigger than Tasmania, home to not many more people and generally rather colder and less hospitable – possessed a race of people who, when Charles Darwin met them in 1834, set bait for fish, nets for seals and snares for birds, used hooks and harpoons, bows and arrows, canoes and clothing – all made with specialised tools and skills. The difference is that the Fuegians were in fairly frequent contact with other people across the Strait of Magellan so that they could relearn lost skills or import new tools from time to time. All it took was an occasional incomer from the mainland to keep technology from regressing.

Networking in the near-east

The lesson is stark. Self-sufficiency was dead tens of thousand years ago. Even the relatively simple lifestyle of a hunter-gatherer cannot exist without a large population exchanging ideas and skills. The importance of this notion cannot be emphasised too strongly. The success of human beings depends crucially, but precariously, on numbers and connections. (#litres_trial_promo) A few hundred people cannot sustain a sophisticated technology: trade is a vital part of the story.

Vast though it is, Australia itself may have suffered from this isolation effect. Recall that it was colonised 45,000 years ago by pioneering beachcombers spreading east from Africa along the shore of Asia. The vanguard of such a migration must have been small in number and must have travelled comparatively light. The chances are they had only a sample of the technology available to their relatives back at the Red Sea crossing. This may explain why Australian aboriginal technology, although it developed and elaborated steadily over the ensuing millennia, was lacking in so many features of the Old World (#litres_trial_promo) – elastic weapons, for example, such as bows and catapults, were unknown, as were ovens. It was not that they were ‘primitive’ or that they had mentally regressed: it was that they had arrived with only a subset of technologies and did not have a dense enough population and therefore a large enough collective brain to develop them much further.