In The Rational Optimist, I argue that the human technological
and economic take-off derives from the invention of exchange and
specialisation some time before 100,000 years ago. When people
began to trade things, ideas could meet and mate, with the result
that a sort of collective brain could form, far more powerful than
individual brains. Cumulative technology could begin to embody this
collective intelligence.
Of course, I did not invent this idea. In keeping with the
theory, I merely put together the ideas of others, notably those of
Joe Henrich (collective intelligence), Rob Boyd (cumulative
culture), Paul Romer (combinatorial ideas), Haim Ofek (the
invention of exchange) and many others.
There was also the important thought that came from Adam Powell, Stephen Shennan and Mark Thomas,
namely that temporary `outbreaks' of new technology in Paleolithic
Africa probably have a demographic explanation. That is, when
population density rose, it resulted in a spurt of innovation; when
population density fell, it resulted in technological regress (as
happened in Tasmania when it was isolated). Technology was
sophisticated, in other words, in proportion to the number of
people networked by exchange to sustain and develop it.