My real father died when I was two years old, so I never knew him. He was a barber in Chicago.

There have been some friendships lost over this. That's the most difficult for me. I find it very uncomfortable to know that I was at one time close friends with someone, and because of jealousies and misunderstandings and so on, these friendships have dissolved.

And what I wanted to do was, I wanted to explore problems and areas where we didn't have answers. In fact, where we didn't even know the right questions to ask.

The right question to ask from a Darwinian prospective is what was it about bipedalism that was so advantageous? Why did it lead to a - why did that adaptation ultimately lead to a species Homo sapiens that has come to dominate the planet today with six and a half billion people?

Normally, we are happy to find a fragment of jaw, a few isolated teeth, a bit of an arm, a bit of a skull. But to find associated body parts is extremely rare.

But what really excited me was the idea that humans had a tremendous pre-history that went back millions of years. I wanted to go to Africa to find some of these creatures.

Evolution explains our biological evolution, but human beings are very unique creatures. As the Dobzhansky said, all animals are unique; humans are the uniquest. And that uniqueness of being human, language, art, culture, our dependency on culture for survival, comes from the combination of traditional biological evolution.