What Makes Us Human?

Scientists have struggled for centuries to pinpoint the qualities that separate human beings from the millions of other animals who have evolved on this planet. David Pogue explores the traits we once thought were uniquely ours - language, tool-making, even laughter - to uncover their evolutionary roots. He traces some of the crucial steps that transformed cave men to accountants - and learns how much of his own DNA came from a Neanderthal ancestor.