I'm absolutely strict about it. When I land, I put my watch right, and I don't care what I feel like, I will go to bed at half past eleven. If that means going to bed early or late, that's what I live by. As soon as you get there, live by that time.

All our environmental problems become easier to solve with fewer people and harder - and ultimately impossible to solve - with ever more people.

Until humanity manages to sort itself out and get a co-ordinated view about the planet, it's going to get worse and worse.

I think the most alarming animals I have encountered are really poisonous snakes.

People are not going to care about animal conservation unless they think that animals are worthwhile.

Climate change will affect the whole of humanity, while terrorist attacks will only affect a small section of humanity. Of course, you wouldn't say that if you were related to someone who had been beheaded or blown up or murdered.

Opponents say natural selection is not a theory supported by observation or experiment; that it is not based on fact; and that it cannot be proved. Well, no, you cannot prove the theory to people who won't believe in it any more than you can prove that the Battle of Hastings took place in 1066. However, we know the battle happened then, just as we know the course of evolution on earth unambiguously shows that Darwin was right.