That's not statistical. Epistasis has not been eliminated as a possibility. There are almost 100 loci, and they looked at two.
The claim of it being selected against is a conclusion, not data. Why would positive selection be required?
I see that as a mere assertion.
me: No, it's associated with particular alleles.
Not in genetics. Alleles are different versions of genes with different sequences. A mutation is the actual event that changes the sequence. IIRC, we are discussing how we know when alleles are preexisting vs. new.
The term you're looking for is "mutant allele," which is fraught with baggage, particularly in clinical genetics. If you don't know which allele was ancestral, you really don't know which allele is mutant, correct?
It matters a great deal educationally and politically, as this is at the heart of so much misunderstanding of Darwinian evolution.
Darwin never mentioned mutation and didn't know what mutations were, but that doesn't present polemicists from stapling the term "mutation" with all its silly baggage (for example, from X-Men films) for laypeople, all over Darwin.
Evolution is much less threatening if you approach it the way Darwin did: organisms in a population differ (fact), at least some of those differences are heritable (fact), so natural selection is common sense.
Do you not see why polemicists are so eager to shift the focus to "random mutations" instead of engaging with what Darwin actually wrote?