British author Matt Ridley knows one thing: Through history, the engine of human progress and prosperity has been, and is, the mating of ideas. The sophistication of the modern world, says Ridley, lies not in individual intelligence or imagination; it is a collective enterprise. In his book The Rational Optimist, Ridley (whose previous works include Genome and Nature via Nurture) sweeps the entire arc of human history to powerfully argue that "prosperity comes from everybody working for everybody else."

It is our habit of trade, idea-sharing and specialization that has created the collective brain which set human living standards on a rising trend. This, he says, "holds out hope that the human race will prosper mightily in the years ahead -- because ideas are having sex with each other as never before."

Watch his 2010 TEDTalk, "When Ideas Have Sex."