A few haircuts.

I would not leave my teenage children to follow an unworthy love. It lasted a month and scarred the family for ever.

I would definitely change the way one or two relationships ended.

I would have honoured my body, I would have lived inside it, cherished it and protected it.

What in a way pleases me and makes me very proud, and I probably shouldn't be, is that I am an honorary fellow of the five oldest academies of the world, all five of them and I don't know whether there's anybody else who can say that.

The interests of a person plays a considerable role. For instance, people who are born naturalists should choose different professions than people who have a spectacular mathematical talent. I think it depends on a person’s talent, what he should choose and what he should love. If you don’t love what you’re doing, you’re not going to do a good job.

One of the answers is that very often I see a statement made by somebody which clearly to me is wrong, and then I work out what is the real right answer, and this happens to me very often.

That is a difficult question to answer because I’ve worked in so many fields. I’ve worked in five different fields. Now which are the most important? In some ways, the development of the biological species concept, which I did not invent, but I certainly was the person that brought it to general knowledge. And the whole field of new systematics — I really am the one who developed it — was one of my major contributions. There’s another one, which is still not yet realized by almost anybody. I have done more, I believe, for the development of a philosophy of biology than any other person.

My father had a wonderful library, and we always bought books galore, and I devoured all the books of explorers that went to various places in the world. I admired what Humboldt had done and Bates and Darwin and the Swedish explorers, Sven Hedin and others. I was dreaming all the time about someday being an explorer, going to the tropics, going to the jungles, seeing new things, discovering strange animals and so forth, but of course it was a dream world.

I always think about things, and if something puzzles me… Well, that of course was one of Darwin’s secrets. Whenever something puzzled him, he tried find a theory. He made a conjecture, as (Karl) Popper would call it, and see if it worked out and that’s true even today.