Matt Ridley explains why humans triumphed rather suddenly, about 45,000 years ago, well after developing big brains, tools, and culture — because they developed collective intelligence through trade:
The explosion of new technologies for hunting and gathering in western Asia around 45,000 years ago, often called the Upper Paleolithic Revolution, occurred in an area with an especially dense population of hunter-gatherers — with a bigger collective brain. Long before the ancestors of modern people first set foot outside Africa, there was cultural progress within Africa itself, but it had a strangely intermittent, ephemeral quality: There would be flowerings of new tool kits and new ways of life, which then faded again.
Recently at Pinnacle Point in South Africa, Curtis Marean of Arizona State University found evidence of seafood-eating people who made sophisticated “bladelet” stone tools, with small blades less than 10 millimeters wide, and who used ochre pigments to decorate themselves (implying symbolic behavior) as long as 164,000 years ago. They disappeared, but a similar complex culture re-emerged around 80,000 years ago at Blombos cave nearby. Adam Powell of University College, London, and his colleagues have recently modeled human populations and concluded that these flowerings are caused by transiently dense populations: “Variation in regional subpopulation density and/or migratory activity results in spatial structuring of cultural skill accumulation.”
The notion that exchange stimulated innovation by bringing together different ideas has a close parallel in biological evolution. The Darwinian process by which creatures change depends crucially on sexual reproduction, which brings together mutations from different lineages. Without sex, the best mutations defeat the second best, which then get lost to posterity. With sex, they come together and join the same team. So sex makes evolution a collective and cumulative process in which any individual can draw on the gene pool of the whole species. And when it comes to gene pools, the species with gene lakes generally do better than the ones with gene ponds — hence the vulnerability of island species to competition with continental ones.
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.
Dense populations don’t produce innovation in other species. They only do so in human beings, because only human beings indulge in regular exchange of different items among unrelated, unmated individuals and even among strangers. So here is the answer to the puzzle of human takeoff. It was caused by the invention of a collective brain itself made possible by the invention of exchange.
Once human beings started swapping things and thoughts, they stumbled upon divisions of labor, in which specialization led to mutually beneficial collective knowledge. Specialization is the means by which exchange encourages innovation: In getting better at making your product or delivering your service, you come up with new tools. The story of the human race has been a gradual spread of specialization and exchange ever since: Prosperity consists of getting more and more narrow in what you make and more and more diverse in what you buy. Self-sufficiency — subsistence — is poverty.
Robert Pirsig, in his excellent “Lila” (the follow-on to his famous “Inquiry into Values” book) draws an analogy between sex/biology and celebrity/culture.
I believe this analogy is a bit more tightly defined than “trade”, and supports the transmission of behaviors within the “collective” mind similarly.
For those who don’t immediately recognize what Pirsig’s famous “Inquiry in Values” book might be, it’s Zen and the Art of Motorcycle Maintenance.