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. 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); 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 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, 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. 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