We are placed in the genus of Homo, which is Latin for man - Homo sapiens: supposedly wise men. I sometimes think - wonder - whether we really are wise men.

What makes us human depends on what place on our evolutionary path we're talking about. If you go back six million years ago, what makes us human is that we were walking upright. That's all. If you go to 2.6 million years ago, it's the fact that we're designing and making stone tools.

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 it really wasn't until three to four years later, when we had an opportunity in the lab to make very detailed observations, and comparisons with other fossil discoveries, that we realized she was a new species of human ancestor.

My chemistry with Salman goes long back, and we have a great equation. Doing a film with him is no less than a dream.

As a practicing neurologist, I place central importance in applying current science to the notion of disease prevention.

I very much enjoyed my career in science. I didn't leave science because I was disillusioned, but felt I'd done my bit for it after about twenty-five years.

Whatever I read went under my skin. I almost devoured the literature, which became like a road to discovery.