Maybe not nearly as long as many anthropologists believe. That's the thesis of Gregory Cochran's controversial book, The 10,000 Year Explosion, which Gregory discusses with ScienceBlogger Razib Khan of Gene Expression in this week's Science Saturday. They also talk about how the evolution of lactose tolerance might explain why Indo-European languages are widespread, whether the invention of helmets changed our skulls, and the way in which survivors of the Black Plague were doubly lucky.
By this logic this economic downturn will only make us smarter. Global warming and the resulting crop destruction will elevate us to Nirvana.