In the caves and rock shelters of the Dordogne region of France, Alan Alda witnesses the spectacular paintings and carvings that date back some 30,000 years, artwork that archeologists once thought to be the first record of people with minds like our own. When this art was created, Europe had already been peopled for hundreds of thousands of years - and thousands of lifetimes - by humans we call Neanderthals. Alan discovers, from visits to sites where Neanderthals once lived, that Neanderthals were tenacious and resourceful. But they appear to have lived in and of the moment; certainly they produced no art, and employed a stone tool technology that changed little over millennia. The people who painted the caves, our ancestors, were strikingly different, possessed of what we are calling the Human Spark, capable not only of art but of innovative technology and symbolic communication. The questions Alan explores: Where and when did the Human Spark first ignite? In these caves, as archeologists have long believed? Or at a much earlier time - and on another continent?

In the futuristic setting of the Laboratory of Neuro Imaging at the University of California, Los Angeles, Alan gets a highly detailed scan of his brain - which for a man in his early 70s, is in remarkably good shape. This image, projected on a huge curved screen behind him, is the starting point for a search within his brain - as well as the brains of others - for the essential components of the Human Spark; a search informed by what the previous two programs have revealed about the attributes that make humans unique.