In this video excerpt from NOVA scienceNOW, correspondent and New York Times technology columnist David Pogue introduces the timeline of human evolution and explores the shapes of hominid heads. Early human ancestors migrated out of Africa and developed into different groups. Neanderthals evolved in Europe and western Asia and existed for hundreds of thousands of years before becoming extinct. Human evolutionary biologist Daniel Lieberman demonstrates how Neanderthal skulls differ from modern human skulls and how head shape may be the key to understanding why Neanderthals did not survive.