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.

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.

When the first fossils began to be found in eastern Africa, in the late 1950s, I thought, what a wonderful marriage this was, biology and anthropology. I was around 16 years old when I made this particular choice of academic pursuit.

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

Commitment, belief and positive attitude are all important if you're going to be a success, whether you're in sports, in business or, as in my case, anthropology.

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.

One has to take initiative in life to achieve what he or she wants.

Scientists are very afraid of being proven wrong.

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.

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.

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.

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.