The Rational Optimist: How Prosperity Evolves

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 it was not that there was no innovation; it was that regress overwhelmed progress.

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. 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. 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 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. 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.

In contrast to Tasmania, Tierra del Fuego – 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. 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 – 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.

The ‘Tasmanian effect’ may also explain why technological progress had been so slow and erratic in Africa after 160,000 years ago. It explains the periodic bursts of modern tools found at South African sites like Pinnacle Point, Blombos Cave and Klasies River. Despite the invention of exchange, the continent was like a patchwork of virtual Tasmanias. As Steve Shennan and his colleagues have calculated, whenever the right combination of (say) seafood, freshwater and fertile savannahs produced local population explosions, technology would have grown sophisticated in proportion to the number of people networked by exchange to sustain and develop it – in proportion to the scale of the collective intelligence. But when a river dried up or deserts advanced and human populations collapsed or shrank, technology would simplify again. Human cultural progress is a collective enterprise and it needs a dense collective brain.

Thus the extraordinary change in technology and cultural tradition that seems to have flourished more than 30,000 years ago in western Asia and the Near East – the so-called Upper Palaeolithic Revolution – may be explained by a dense population. Fed by an increasingly intensive and vegetarian hunter-gathering lifestyle, and with close contact between tribes, the people of south-west Asia were in a position to accumulate more and more skills and technologies than any previous human populations. A large, interconnected population meant faster cumulative invention – a surprising truth even to this day, as Hong Kong and Manhattan islands demonstrate. As the economist Julian Simon put it, ‘population growth leading to diminishing returns is fiction; the induced increase in productivity is scientific fact’. And one of those inventions was farming, which is the subject of the next chapter.

It is right to end the hunter-gatherer chapter, though, by remembering what happened to the Tasmanians. In the early 1800s, white sealers began to arrive along the island’s coasts and it was not long before the Tasmanians were eagerly meeting the sealers to trade with them, proving that 10,000 years of limited exchange had done nothing to dampen their innate enthusiasm for barter. The sealers’ dogs were especially sought after, being deerhounds that could easily run down kangaroos. In exchange, sad to relate, Tasmanians sold women to the sealers as concubines. Once white farmers arrived, relations between the two peoples deteriorated and eventually the whites sent bounty hunters to kill the natives, then rounded up the survivors and exiled them to Flinders Island, where they eked out their last days in misery.