What is the nature of human uniqueness? Where did "The Human Spark" ignite, and when? And perhaps most tantalizingly, why? In this three-part series, Alan Alda takes these questions personally, visiting with dozens of scientists on three continents, and participating directly in many experiments -- including the detailed examination of his own brain. Bringing his trademark humor and curiosity to face-to-face conversations with leading researchers, he seeks "The Human Spark" -- from archaeologists finding clues in the fossilized bones and tools of our ancestors, to primatologists studying our nearest living relatives to explore what we have in common and what sets us apart, to neuroscientists peering into his mind with the latest brain scanning technologies. (Source: PBS)