It's been proven by quite a few studies that plants are good for our psychological development. If you green an area, the rate of crime goes down. Torture victims begin to recover when they spend time outside in a garden with flowers. So we need them, in some deep psychological sense, which I don't suppose anybody really understands yet.

I do not want to discuss evolution in such depth, however, only touch on it from my own perspective: from the moment when I stood on the Serengeti plains holding the fossilized bones of ancient creatures in my hands to the moment when, staring into the eyes of a chimpanzee, I saw a thinking, reasoning personality looking back. You may not believe in evolution, and that is all right. How we humans came to be the way we are is far less important than how we should act now to get out of the mess we have made for ourselves.

We have so far to go to realize our human potential for compassion, altruism, and love.

My mission is to create a world where we can live in harmony with nature. And can I do that alone? No. So there is a whole army of youth that can do it. So I suppose my mission is to reach as many of those young people as I can through my own efforts.

I feel a desperation to make people see what we are doing to the environment, what a mess we are making of our world. At this point, the more people I reach, the more I accomplish. ... I miss Gombe and my wonderful years in the forest But if I were to go back to that, I wouldn't feel I was doing what I should be doing.

We can learn to suppress our feelings for other reasons.

To me, cruelty is the worst of human sins. Once we accept that a living creature has feelings and suffers pain, then by knowingly and deliberately inflicting suffering on that creature, we are guilty, whether it be human or animal.