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.

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.

Scientists are very afraid of being proven wrong.

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.

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

Lucy brought with her an image of our human ancestors that you don't get when you find a jaw or an arm bone or a leg bone. Here was 40 percent of a single skeleton.

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.