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

The whole of science, and one is tempted to think the whole of the life of any thinking man, is trying to come to terms with the relationship between yourself and the natural world. Why are you here, and how do you fit in, and what's it all about.

I remember when we were in the World Cup in Australia and I had to win the singles against Tony Payne, best of seven legs, to win it. I was 2-0 down but ended up beating him I suffer much less than many of my colleagues. I am perfectly able to go to Australia and film within three hours of arrival.

In the West, that's what's happening. The birth rate has been dropping steadily and still is. But there is still a vast amount of the world where that's not the case. And that is where the big population growth is taking place.

Apart from anything else, I am designed by evolution, like we all are: if we see a little thing like that, big eyes, tiny nose, we go 'aaah'. That's what evolution does. We are programmed to do that. So to find babies the most amazing, isn't surprising, I don't think.

Natural history is not about producing fables.

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.