The Rational Optimist: How Prosperity Evolves

Erectus hominids, in other words, had almost everything we might call human: two legs, two hands, a big brain, opposable thumbs, fire, cooking, tools, technology, cooperation, long childhoods, kindly demeanour. And yet there was no sign of cultural take-off, little progress in technology, little expansion of range or niche.

Homo dynamicus

Then there appeared upon the earth a new kind of hominid, which refused to play by the rules. Without any changes in its body, and without any succession of species, it just kept changing its habits. For the first time its technology changed faster than its anatomy. This was an evolutionary novelty, and you are it.

When this new animal appeared is hard to discern, and its entrance was low-key. Some anthropologists argue that in east Africa and Ethiopia the toolkit was showing signs of change as early as 285,000 years ago. Certainly, by at least 160,000 years ago a new, small-faced ‘sapiens’ skull was being worn on the top of the spine in Ethiopia. Around the same time at Pinnacle Point in South Africa, people – yes, I shall call them people for the first time – were cooking mussels and other shellfish in a cave close to the sea as well as making primitive ‘bladelets’, small flakes of sharp stone, probably for hafting on to spears. They were also using red ochre, perhaps for decoration, implying thoroughly modern symbolic minds.

This was during the ice age before last, when Africa was mostly a desert. And yet apparently nothing much came of this experiment. Consistent evidence of smart behaviour and a fancy toolkit peters out again. Genetic evidence suggests human beings were still rare even in Africa, eking out a precarious existence in pockets of savannah woodland when it was dry, or possibly on the margins of lakes and seas. In the Eemian interglacial period of 130,000–115,000 years ago, the climate grew warmer and much wetter and sea level rose. Some skulls from what is now Israel suggest that a few slender-headed Africans did begin to colonise the Middle East towards the end of the Eemian, before a combination of cold weather and Neanderthals drove them back again. It was during this mild spell that a fancy new toolkit first appeared in caves in what is now Morocco: flakes, toothed scrapers and retouched points. One of the most extraordinary clues comes in the form of a simple estuarine snail shell called Nassarius. This little winkle keeps popping up in archaeological sites, with unnatural holes in its shells. The oldest certain Nassarius find is at Grottes des Pigeons near Taforalt in Morocco, where forty-seven perforated shells, some smeared with red ochre, date from certainly more than 82,000 years ago and perhaps as much as 120,000 years ago. Similar shells, harder to date, have been found at Oued Djebanna in Algeria and Skhul in Israel, and perforated shells of the same genus but a different species are found at Blombos cave in South Africa from about 72,000 years ago along with the earliest bone awls. These shells were surely beads, probably worn on a string. Not only do they hint at a very modern attitude to personal ornament, symbolism or perhaps even money; they also speak eloquently of trade. Taforalt is 25 miles and Oued Djebanna 125 miles from the nearest coast. The beads probably travelled hand to hand by exchange. Likewise, there are hints from east Africa and Ethiopia that the volcanic glass known as obsidian may have begun to move over long distances around this time too, or even earlier, presumably by trade, but the dates and sources are still uncertain.

Just across the strait of Gibraltar from where these bead-wearing, flake-making people lived were the ancestors of Neanderthals, whose brains were just as big but who showed no signs of making beads or flake tools, let alone doing long-distance trade. There was clearly something different about the Africans. Over the next few tens of millennia there were sporadic improvements, but no great explosion. There may have been a collapse of human populations. The African continent was plagued by ‘megadroughts’ at this time, during which desiccating winds blew the dust of extensive deserts into Lake Malawi, whose level dropped 600 metres. Only well after 80,000 years ago, so genetic evidence attests, does something big start to happen again. This time the evidence comes from genomes, not artefacts. According to DNA scripture, it was then that one quite small group of people began to populate the entire African continent, starting either in East or South Africa and spreading north and rather more slowly west. Their genes, marked by the L3 mitochondrial type, suddenly expanded and displaced most others in Africa, except the ancestors of the Khoisan and pygmy people. Yet even now there was no hint of what was to come, no clue that this was anything but another evolutionary avatar of a precariously successful predatory ape. The new African form, with its fancy tools, ochre paint and shell-bead ornaments, might have displaced its neighbours, but it would now settle down to enjoy its million years in the sun before gracefully giving way to something new. This time, however, some of the L3 people promptly spilled out of Africa and exploded into global dominion. The rest, as they say, is history.

Starting to barter

Anthropologists advance two theories to explain the appearance in Africa of these new technologies and people. The first is that it was driven by climate. The volatility of the African weather, sucking human beings into deserts in wet decades and pushing them out again in dry ones, would have placed a premium on adaptability, which in turn selected for new capabilities. The trouble with this theory is first that climate had been volatile for a very long time without producing a technologically adept ape, and second that it applies to lots of other African species too: if human beings, why not elephants and hyenas? There is no evidence from the whole of the rest of biology that desperate survival during unpredictable weather selects intelligence or cultural flexibility. Rather the reverse: living in large social groups on a plentiful diet both encourages and allows brain growth.

The second theory is that a fortuitous genetic mutation triggered a change in human behaviour by subtly altering the way human brains were built. This made people fully capable of imagination, planning, or some other higher function for the first time, which in turn gave them the capacity to make better tools and devise better ways of making a living. For a while, it even looked as if two candidate mutations of the right age had appeared – in the gene called FOXP2, which is essential to speech and language in both people and songbirds. Adding these two mutations to mice does indeed seem to change the flexibility of wiring in their brain in a way that may be necessary for the rapid flicker of tongue and lung that is called speech, and perhaps coincidentally the mutations even change the way mice pups squeak without changing almost anything else about them. But recent evidence confirms that Neanderthals share the very same two mutations, which suggests that the common ancestor of Neanderthals and modern people, living about 400,000 years ago, may have already been using pretty sophisticated language. If language is the key to cultural evolution, and Neanderthals had language, then why did the Neanderthal toolkit show so little cultural change?

Moreover, genes would undoubtedly have changed during the human revolution after 200,000 years ago, but more in response to new habits than as causes of them. At an earlier date, cooking selected mutations for smaller guts and mouths, rather than vice versa. At a later date, milk drinking selected for mutations for retaining lactose digestion into adulthood in people of western European and East African descent. The cultural horse comes before the genetic cart. The appeal to a genetic change driving evolution gets gene-culture co-evolution backwards: it is a top-down explanation for a bottom-up process.

Besides, there is a more fundamental objection. If a genetic change triggered novel human habits, why do its effects appear gradually and erratically in different places at different times but then accelerate once established? How could the new gene have a slower effect in Australia than in Europe? Whatever the explanation for the modernisation of human technology after 200,000 years ago, it must be something that gathers pace by feeding upon itself, something that is auto-catalytic.

As you can tell, I like neither theory. I am going to argue that the answer lies not in climate, nor genetics, nor in archaeology, nor even entirely in ‘culture’, but in economics. Human beings had started to do something to and with each other that in effect began to build a collective intelligence. They had started, for the very first time, to exchange things between unrelated, unmarried individuals; to share, swap, barter and trade. Hence the Nassarius shells moving inland from the Mediterranean. The effect of this was to cause specialisation, which in turn caused technological innovation, which in turn encouraged more specialisation, which led to more exchange – and ‘progress’ was born, by which I mean technology and habits changing faster than anatomy. They had stumbled on what Friedrich Hayek called the catallaxy: the ever-expanding possibility generated by a growing division of labour. This is something that amplifies itself once begun.

Exchange needed to be invented. It does not come naturally to most animals. There is strikingly little use of barter in any other animal species. There is sharing within families, and there is food-for-sex exchange in many animals including insects and apes, but there are no cases in which one animal gives an unrelated animal one thing in exchange for a different thing. ‘No man ever saw a dog make fair and deliberate exchange of a bone with another dog,’ said Adam Smith.

I need to digress here: bear with me. I am not talking about swapping favours – any old primate can do that. There is plenty of ‘reciprocity’ in monkeys and apes: you scratch my back and I scratch yours. Or, as Leda Cosmides and John Tooby put it, ‘One party helps another at one point in time, in order to increase the probability that when their situations are reversed at some (usually) unspecified time in the future, the act will be reciprocated.’ Such reciprocity is an important human social glue, a source of cooperation and a habit inherited from the animal past that undoubtedly prepared human beings for exchange. But it is not the same thing as exchange. Reciprocity means giving each other the same thing (usually) at different times. Exchange – call it barter or trade if you like – means giving each other different things (usually) at the same time: simultaneously swapping two different objects. In Adam Smith’s words, ‘Give me that which I want, and you shall have this which you want.’

Barter is a lot more portentous than reciprocity. After all, delousing aside, how many activities are there in life where it pays to do the same thing to each other in turn? ‘If I sew you a hide tunic today, you can sew me one tomorrow’ brings limited rewards and diminishing returns. ‘If I make the clothes, you catch the food’ brings increasing returns. Indeed, it has the beautiful property that it does not even need to be fair. For barter to work, two individuals do not need to offer things of equal value. Trade is often unequal, but still benefits both sides. This is a point that nearly everybody seems to miss. In the grasslands of Cameroon, for example, in past centuries the palm-oil producers, who lived on the periphery of the region on the poorest soils, worked hard to produce a low-value product that they exchanged for cereal, livestock and iron with their neighbours. On average it took them thirty days to afford the price of an iron hoe that had cost its makers just seven person-days of work. Yet palm oil was still the most profitable product they could make on their own land and with their own resources. The cheapest way for them to get an iron hoe was to make more palm oil. Or imagine a Trobriand island tribe on the coast that has ample fish and an inland tribe that has ample fruit: as long as two people are living in different habitats, they will value what each other has more than what they have themselves, and trade will pay them both. And the more they trade, the more it will pay them to specialise.

Evolutionary psychologists have assumed that it is rare for conditions to exist in which two people simultaneously have value to offer to each other. But this is just not true, because people can value highly what they do not have access to. And the more they rely on exchange, the more they specialise, which makes exchange still more attractive. Exchange is therefore a thing of explosive possibility, a thing that breeds, explodes, grows, auto-catalyses. It may have built upon an older animal instinct of reciprocity, and it may have been greatly and uniquely facilitated by language – I am not arguing that these were not vital ingredients of human nature that allowed the habit to get started. But I am saying that barter – the simultaneous exchange of different objects – was itself a human breakthrough, perhaps even the chief thing that led to the ecological dominance and burgeoning material prosperity of the species. Fundamentally, other animals do not do barter.

I still don’t quite know why, but I have a lot of trouble getting this point across to both economists and biologists. Economists see barter as just one example of a bigger human habit of general reciprocity. Biologists talk about the role that reciprocity played in social evolution, meaning ‘do unto others as they do unto you’. Neither seems to be interested in the distinction that I think is vital, so let me repeat it here once more: at some point, after millions of years of indulging in reciprocal back-scratching of gradually increasing intensity, one species, and one alone, stumbled upon an entirely different trick. Adam gave Oz an object in exchange for a different object. This is not the same as Adam scratching Oz’s back now and Oz scratching Adam’s back later, or Adam giving Oz some spare food now and Oz giving Adam some spare food tomorrow. The extraordinary promise of this event was that Adam potentially now had access to objects he did not know how to make or find; and so did Oz. And the more they did it, the more valuable it became. For whatever reason, no other animal species ever stumbled upon this trick – at least between unrelated individuals.

Do not take my word for it. The primatologist Sarah Brosnan tried to teach two different groups of chimpanzees about barter and found it very problematic. Her chimps preferred grapes to apples to cucumbers to carrots (which they liked least of all). They were prepared sometimes to give up carrots for grapes, but they almost never bartered apples for grapes (or vice versa), however advantageous the bargain. They could not see the point of giving up food they liked for food they liked even more. Chimpanzees and monkeys can be taught to exchange tokens for food, but this is a long way from spontaneously exchanging one thing for another: the tokens have no value to the chimpanzees, so they are happy to give them up. True barter requires that you give up something you value in exchange for something else you value slightly more.

This is reflected in the ecology of wild chimpanzees. Whereas in human beings, each sex eats ‘not only from the food items they have collected themselves, but from their partners’ finds,’ says Richard Wrangham, ‘not even a hint of this complementarity is found among nonhuman primates.’ It is true that male chimps hunt monkeys more than females do and that having killed a monkey, a male sometimes allows others to share it if they beg to, especially a fertile female or a close partner to whom he owes a favour. But the one thing you do not see is trade of one food for another. There is never barter of meat for nuts. The contrast with human beings, who show an almost obsessive interest not just in sharing food with each other from an early age, but in swapping one item for another, is striking. Birute Galdikas reared a young orang-utan in her home alongside her daughter Binti, and was struck by the contrasting attitudes to food sharing of the two infants. ‘Sharing food seemed to give Binti great pleasure,’ she wrote. ‘In contrast, Princess, like any orang-utan would beg, steal and gobble food at every opportunity’.

My argument is that this habit of exchanging, this appetite for barter, had somehow appeared in our African ancestors some time before 100,000 years ago. Why did human beings acquire a taste for barter as other animals did not? Perhaps it has something to do with cooking. Richard Wrangham makes a persuasive case that control of fire had a far-reaching effect on human evolution. Beyond making it safe to live on the ground, beyond liberating human ancestors to grow big brains on high-energy diets, cooking also predisposed human beings to swapping different kinds of food. And that maybe got them bartering.

Hunting for gathering

As the economist Haim Ofek has argued, fire itself is hard to start, but easy to share; likewise cooked food is hard to make but easy to share. The time spent in cooking is subtracted from the time spent in chewing: wild chimpanzees spend six hours or more each day just masticating their food. Carnivores might not chew their meat (they are often in a hurry to eat before it is stolen), but they spend hours grinding it in muscular stomachs, which comes to much the same thing. So cooking adds value: the great advantage of cooked food is that though it takes longer to prepare than raw food, it takes just minutes to eat, and this means that somebody else can eat as well as the person who prepares it. A mother can feed her children for many years. Or a woman can feed a man.

In most hunter-gatherers, women spend long hours gathering, preparing and cooking staple foods while men are out hunting for delicacies. There is, incidentally, no hunter-gatherer society that dispenses with cooking. Cooking is the most female-biased of all activities, the only exceptions being when men prepare some ritual feasts or grill a few snacks while out on the hunt. (Does this ring any modern bells? Fancy chefs and barbecuing are the two most masculine forms of cooking today.) On average, across the world, each sex contributes similar quantities of calories, though the pattern varies from tribe to tribe: in Inuits, for example, most food is obtained by men, whereas in the Kalahari Khoisan people, most is gathered by women. But – and here is the crucial point – throughout the human race, males and females specialise and then share food.

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’. The two sexes move ‘through the same habitat, making strikingly different decisions about how to obtain resources within that habitat, 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; 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.’

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.