[Q] [RA] Fisher, at the beginning of the Genetical Theory [of Natural Selection], discusses how Darwin was closer to it than one might have thought. He was definitely on to the idea that sex was inherited in an all or none way, so he... he probably wouldn't have needed much prompting from Mendel.

No. Curiously enough, his cousin, Francis Galton, was awful close too, and clearly Weismann was very close. Weismann almost reinvented Mendel's Laws a priori, actually, if only he'd been prepared to believe the world was a bit simpler than he did, he'd have got Mendel's Laws a priori with no experiments at all - but he didn't quite.

[Q] Fisher thought they ought to have been invented a priori.

Well, they very nearly were. Weismann gets the whole thing, he says... he talks about Ids, not genes, he gets the whole thing, except that he cannot believe the world is so simple that there's just one copy of each gene in the gamete and two in the zygote. And he does it, I can't remember, for a hexadecaploid, something with 16 copies of every gene. And, of course, the thing becomes horrendously complicated. If only he'd said, the simple way is to have one copy each, he'd have got Mendel's Laws. Sad, really. But I think, obviously, the fact that Haldane understood something and taught his student, doesn't mean to say that everybody at that time did. But I didn't see any signs of incomprehension. I mean, there were people around who were in the old morphological trap who didn't actually see this was interesting. You know, that's always the way. And there were fights about grants and editorships and all that sort of... the sociological stuff, but there was no intellectual difficulty.