The most extraordinary thing about trying to piece together the missing links in the evolutionary story is that when you do find a missing link and put it in the story, you suddenly need all these other missing links to connect to the new discovery. The gaps and questions actually increase - it's extraordinary.

The human population can no longer be allowed to grow in the same old uncontrollable way. If we do not take charge of our population size, then nature will do it for us and it is the poor people of the world who will suffer most

I'm no longer sceptical. I no longer have any doubt at all. I think climate change is the major challenge facing the world.

I like animals. I like natural history. The travel bit is not the important bit. The travel bit is what you have to do in order to go and look at animals.

All the modern devices we have enable us to investigate things and have enabled us to do better.

I had a huge advantage when I started 50 years ago - my job was secure. I didn't have to promote myself. These days there's far more pressure to make a mark, so the temptation is to make adventure television or personality shows. I hope the more didactic approach won't be lost.

How could I look my grandchildren in the eye and say I knew what was happening to the world and did nothing.