So at one point I decided I would change to become evolutionary biologist instead of immunogeneticist. In practical terms it meant that the fantastic mouse house that I had in Tübingen, which I think was at that time the best in Europe and certainly in terms of the number of different genetic variants that we were carrying and also in terms of the size, which helped I think a lot of other institutions in Europe because we were able to supply them with the variants that they needed... so at one point it was decided that it would be turned into a fish house because fish was one of the chosen animals that we decided immunology... evolutionary biology could be studied. So this... although it involved considerable expense was done within a very short time and in a very short time it functioned as a fish house again stuffed with a large number of variants that we were needing.

The evolutionary biology I had in mind was... it started from the H2 actually, from the study of the polymorphism and the trans-species evolution of the polymorphism... led me naturally to questions which concerned how species arise... speciation... one of the very basic questions in evolutionary biology many people think, or the lay people usually think that has been solved by Darwin, but in fact it is still... it was still not known very little about the mechanics of speciations. There were many speculations, many theories, but hard facts were quite limited at that time, and I'll explain how the H2 system... the MHC system in this case... led us to these studies. But in addition to speciation, I also decided to follow the evolution of the MHC, which was very natural and by extension also the evolution of the immune system in general.

The MHC was studied until then in mice and humans and a few other mammals, but almost nothing was known about other vertebrate groups.  But slowly other people got interested in it too and so soon were fish MHC cloned and MHC of other vertebrate classes. The question was how does the MHC look like in non-mammals or even in other mammals because I think we were very biased in our views of the MHC from the mouse and humans, although there already were some differences so it could be expected that there will be even major other differences in other groups. But the main question was how did it originate, the MHC, were did it come from, and how did its organisation change during the evolution?