People like to wonder – why are humans the dominant life form on the planet? Why are we special? Even though humans are probably not as special as we like to think, there is one thing that seems to separate us from other animals: culture. Culture, trade, speech, sociality. These seem to be the ingredients for human dominance and ‘intelligence’. We are better at some cognitive tasks, but was that enough? Did we get smart or just get together? I tend to think the answer is that we got together:
Scientists have so far been looking for the answer to this riddle in the wrong place: inside human heads. Most have been expecting to find a sort of neural or genetic breakthrough that sparked a “big bang of human consciousness,” an auspicious mutation so that people could speak, think or plan better, setting the human race on the path to continuous and exponential innovation.
But the sophistication of the modern world lies not in individual intelligence or imagination. It is a collective enterprise. Nobody—literally nobody—knows how to make the pencil on my desk (as the economist Leonard Read once pointed out), let alone the computer on which I am writing. The knowledge of how to design, mine, fell, extract, synthesize, combine, manufacture and market these things is fragmented among thousands, sometimes millions of heads. Once human progress started, it was no longer limited by the size of human brains. Intelligence became collective and cumulative.
…Agriculture was invented where people were already living in dense trading societies. The oldest farming settlements of all in what is now Syria and Jordan are situated at oases where trade routes crossed, as proved by finds of obsidian (volcanic glass) tools from Cappadocia. When farmers first colonized Greek islands 9,000 years ago they relied on imported tools and exported produce from the very start. Trade came before—and stimulated—farming.
It is precisely the same in cultural evolution. Trade is to culture as sex is to biology. Exchange makes cultural change collective and cumulative. It becomes possible to draw upon inventions made throughout society, not just in your neighborhood. The rate of cultural and economic progress depends on the rate at which ideas are having sex.
…This theory neatly explains why some parts of the world lagged behind in their rate of cultural evolution after the Upper Paleolithic takeoff. Australia, though it was colonized by modern people 20,000 years earlier than most of Europe, saw comparatively slow change in technology and never experienced the transition to farming. This might have been because its dry and erratic climate never allowed hunter-gatherers to reach high enough densities of interaction to indulge in more than a little specialization.
Where population falls or is fragmented, cultural evolution may actually regress. A telling example comes from Tasmania, where people who had been making bone tools, clothing and fishing equipment for 25,000 years gradually gave these up after being isolated by rising sea levels 10,000 years ago. Joe Henrich of the University of British Columbia argues that the population of 4,000 Tasmanians on the island constituted too small a collective brain to sustain, let alone improve, the existing technology.
There is some theoretical support for the get-together hypothesis. The authors extend a previous model of cultural transmission to include a more realistic structured metapopulation, among other things. In their model, each individual attempts to learn from the most-skilled individual, but an imperfect learning process leads to an average net loss in skill. However, individual errors (“inaccurate inferences”) occasionally allow some learners to acquire an even greater skill during transmission. The world is divided into subpopulations that are connected by a Gaussian random-walk migratory activity.
Whereas the earlier model suggested that population size was the primary variable that fixed the average cultural skill, the metapopulation analysis indicated that this was only true for small numbers of subgroups (~<50). For larger numbers of subgroups (states, tribes, etc.) the skill accumulation depends on the degree of interaction between subgroups. In fact, the benefits of migration/trade were highest for cultural skills with the most complexity. Perhaps we should be thankful we outbred the neanderthals.
Update: And of course a paper comes out on just this hypothesis! They show how population size predicts technological complexity in Oceania. When population drops, technology drops. Here is a good post about the paper, and here is another.