"Scientists have identified perhaps the most crucial genetic region that makes us human. By comparing human DNA with that of chimpanzees and other animals they have found the region of the genome subjected to the strongest natural selection since we shared a common ancestor with chimps. … This region differs by just two changes between chimps and chickens, which shared a common ancestor around 310 million years ago. But since humans and chimps split 5 million years ago there have been 18 changes."
—The Guardian, Aug. 17, 2006