This was the first indication that there is sharing... real sharing of alleles between two different species. Now, that presented a problem and I struggled with that problem for a long time... not a long time but several years I would say. Well, that's a long time. Normally everybody would argue, and everybody did argue as it turned out... would argue that this must be so-called convergence.  That these alleles arose independently in the two strains, or two species. I had difficulty with that explanation and I was not willing to accept it but I was thinking what could be the other, the alternative... what better explanation? It now... the solution now seems very logical and obvious, but it's a good example of what difficulties you face. The blocks in your mind that prevented you to see the obvious solution, and I remember waking up one morning very precisely and suddenly it came to me, you are stupid, this is very simple. In my mind was polymorphism always associated with the species. There was no way of sharing polymorphism between species but it occurred to me well, what if that is not true and actually the alleles arose before the species separated and they just remained in both species. That's why they have the same alleles so that polymorphism could be much older than the conventional wisdom that all geneticists were willing to... never doubt, was actually not true. So the conventions are often a very big hindrance in finding the right explanation, which in this case was certainly so.