Maybe Trade, Not Brain Size, Is What Led To Human Success

See The ancient cloud by Matt Ridely.

"There was no sudden change in brain size 200,000 years ago. We Africans—all human beings are descended chiefly from people who lived exclusively in Africa until about 65,000 years ago—had slightly smaller brains than Neanderthals, yet once outside Africa we rapidly displaced them (bar acquiring 2.5% of our genes from them along the way).

And the reason we won the war against the Neanderthals, if war it was, is staring us in the face, though it remains almost completely unrecognized among anthropologists: We exchanged. At one site in the Caucasus there are Neanderthal and modern remains within a few miles of each other, both from around 30,000 years ago. The Neanderthal tools are all made from local materials. The moderns' tools are made from chert and jasper, some of which originated many miles away. That means trade.

Evidence from recent Australian artifacts shows that long-distance movement of objects is a telltale sign of trade, not migration. We Africans have been doing this since at least 120,000 years ago. That's the date of beads made from marine shells found a hundred miles inland in Algeria. Trade is 10 times as old as agriculture.

At first it was a peculiarity of us Africans. It gave us the edge over Neanderthals in their own continent and their own climate, because good ideas can spread through trade. New weapons, new foods, new crafts, new ornaments, new tools. Suddenly you are no longer relying on the inventiveness of your own tribe or the capacity of your own territory. You are drawing upon ideas that occurred to anybody anywhere anytime within your trading network.

In the same way, today, American consumers do not have to rely only on their own citizens to discover new consumer goods or new medicines or new music: The Chinese, the Indians, the Brazilians are also able to supply them.

That is what trade does. It creates a collective innovating brain as big as the trade network itself. When you cut people off from exchange networks, their innovation rate collapses. Tasmanians, isolated by rising sea levels about 10,000 years ago, not only failed to share in the advances that came after that time—the boomerang, for example—but actually went backwards in terms of technical virtuosity. The anthropologist Joe Henrich of the University of British Columbia argues that in a small island population, good ideas died faster than they could be replaced. Tierra del Fuego's natives, on a similarly inhospitable and small land, but connected by trading canoes across the much narrower Magellan strait, suffered no such technological regress. They had access to a collective brain the size of South America."