As a young man in Russia he was a naturalist, in fact he was a taxonomist of beetles, of ladybird beetles, and worked on their taxonomy, on their population structure, on their geographic variation and all that. And after about… when he had reached the age of about 27 and had for at least 10 years done such studies, he was invited to come to the United States with the help of a… a Rockefeller grant, and he went to Morgan's lab in Pasadena and he now became acquainted with the thinking and the methods of the geneticists. And after he'd done that for about eight years or so, or nine, he suddenly saw how he could put the two things together. And when he gave his lectures, these Jesup lectures in 1936, he provided the basis… then published in 1937 in a book called Genetics and the Origin of Species, he provided the necessary basis, and he showed – and through his publication it became quite clear – that there had been two major areas in evolutionary biology. I mentioned already but I deliberately repeat it once more: the one area, that of adaptation which the geneticists studied, and the other one, the area of organic diversity which the naturalists had studied. But now he showed that there was no conflict between the two areas and that by explaining geographic speciation and all that you could bring the whole stuff together. Much of his account was rather, what shall I say, not skimpy, but… just barely indicating what it was all about, and it was my task in my book Systematics and the Origin of Species to work it out in much greater detail, which I did. Well, Dobzhansky and I, we became very close friends because very soon after that he got a call to come to Columbia University in 1939. And he was in Columbia in 1939 until… I don't know what year, but anyhow, when I left for Harvard  in 1953 he was still a professor in New York City and we only lost a little bit contact with each other after we were geographically widely separated. Now I don't… didn't always go along with Dobzhansky, Dobzhansky was very much influenced by Sewall Wright in emphasizing… non-adaptive evolution, evolution by pure chance. Well, I agree there is quite a bit pure chance in evolution, but the examples that he chose to defend are practically all turned out that in the long run it was selection, after all, that had caused the differences were insincere. And I disagreed on the human blood groups, he said they were neutral and I always said they have some selective significance, and I think the majority of authors now agree with that.