[chubot]

There are genetic differences between groups, but claim (a) is that there are such differences that contribute (substantively) to different outcomes -- as you wrote yourself. I don't know of any such evidence. It's controversial to say the least, but if you are engaging me in a discussion, you have the burden of proof on that point.

As mentioned, I don't really care for these types of discussions, because either way, it's not going to lead me to change my actions. My original motivation was to see what moldbug thinks of Jared Diamond's work (i.e. if he tries to refute it)

(a) and (b) aren't exclusive, but it could be that one contributes vastly more to the observed outcomes than the other. I happen to believe that this is the case with (b), as Jared Diamond explains. There is just much less evidence supporting (a) compared to that supporting (b).

I think you misread my last statement. Providing evidence for b means that you can't apply the argument that if b were false, then a. They are not exclusive, but at least one of them is necessary. I would assume (b) is false without evidence as well.

[lexcorvus]

claim (a) is that there are such differences that contribute (substantively) to different outcomes

That is not claim (a). Claim (a) is that there are genetic factors in group differences, but makes no assertion about their magnitude. You believe that genetic factors make at most a small contribution. You may well be right. But you have offered no evidence for this assertion, and the burden of proof is on you to show it.

I would assume (b) is false without evidence as well.

Given that different groups live in manifestly different physical and social environments, this assumption is also wrong. The null hypothesis is that both (a) and (b) contribute; the burden of proof in both cases is on those who think one or the other is false. Confusing this issue, whether intentionally or unintentionally, is perhaps the most common source of crimestop on this subject. (Not that I blame you; as a crimethinker myself, I can assure you that volunteer Thought Police are everywhere, even—perhaps especially—on HN.)

Of course, in reality the discussion usually goes something like this:

"There might be genetic factors accounting for differences in group outcomes."

"I doubt it, but even if there are such factors, they're small."

"How do you know they're small?"

"Well, how do you know they're not?"

[Caught in trap] "I don't. So let's investigate the magnitude of the effect by examining the direct evidence…"

"That's racist."