Since modern humans emerged from the evolutionary brambles of our ancient ancestry, our bodies and minds have been transforming under the pressures of natural and sexual selection. But what of human intelligence? Has our cognitive ability risen steadily since our forebears knapped the first stone tools? Or are our smartest days behind us?
Gerald Crabtree, a geneticist at Stanford University in California, bets on the latter. He believes that if an average Greek from 1,000 BC were transported to modern times, he or she would be one of the brightest among us. Our intellectual prowess has probably been sliding south since the invention of farming and the rise of high-density living that it allowed, he claims.