As an undergraduate, I had an opportunity to go on a number of archeological digs. So I had experience excavating, digging up remains of ancient Indian villages in the Midwest and in the Southwest.

I think that many of my ideas are correct, but I'll bet you, before my death other discoveries will be made that will prompt me to alter various ideas I have about human evolution.

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.

In our case, finding a Lucy is unique. No one will ever find another Lucy. You can't order one from a biological supply house. It's a unique discovery, a unique specimen.

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.

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?

Scientists are very afraid of being proven wrong.