For those who have experienced the joy of being alone with nature there is really little need for me to say much more; for those who have not, no words of mine can ever describe the powerful, almost mystical knowledge of beauty and eternity that come, suddenly, and all unexpected.

I see that within each human being there are two extremes: there's the loving, the passionate, altruistic side that has evolved with us, and then there's the violent, brutal side that has evolved with us. The question for each individual is: which side is going to come out on top?

Chimps taught us we're not separated from the animal kingdom, we're a part of it.

Even in chimps there is true altruistic behaviour; behaviour that doesn't fit into the sociobiological model that says you either help a close relative and thereby your own genes, or you help somebody else now in return for their help in the future. When a very high-ranking male chimpanzee rescues a little orphan, saving his life, that kind of explanation doesn't work.

I thought my life was mapped out. Research, living in the forest, teaching and writing. But in '86 I went to a conference and realised the chimpanzees were disappearing. I had worldwide recognition and a gift of communication. I had to use them.

What makes us human, I think, is an ability to ask questions, a consequence of our sophisticated spoken language.

The best relationship you can have with a chimpanzee is total mutual trust.