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by SubmarineClub 62 days ago
How exactly does that contradict the concept of fitness?

Several examples from the paper are exactly that. E.g dark skin was better for survival in Africa, but as populations moved north light skin was strongly selected for. Given the levels of sunlight in Europe, lighter skin increased fitness.
1 comments
taeric 62 days ago
It is against the idea that the beneficial traits will survive to the present. It could be that there was some trait/gene that was absolutely needed for survival in the past, that flat out became irrelevant and dropped off before the present.

That is, it is not an argument against any of the traits that are present. Is why I said the problem is with how it was stated. But you do not have everything with you to provide evidence for all of the things necessary for you to have gotten here. At best, you have evidence that nothing you have with you prevented you from getting here.

That make sense? I grant that pulling it back up, I see the comment I was responding to was hedged. My concern is largely against the idea that things that "were selected for" in the past can be determined by evidence. I'm not convinced it can't be. But I find this presentation of it to be somewhat weak.

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MarkusQ 62 days ago
More to the point, TFA is specifically addressing the issue (which is part of what makes it a big deal).

They aren't saying "we see these things now, so they must be good" but rather things like "we see these selected for from 9kya to 3kya, but from then to the present they were selected against"; they are specifically looking at how apparent selective pressures changed over time.

> the idea that things that "were selected for" in the past can be determined by evidence

When the evidence is a copious selection of ancient genomes, distributed over both space and time, they certainly can be.

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taeric 62 days ago
Apologies, I only meant my gripe with the comment I was responding to. Is why I put "as stated." I meant that to be that I was not arguing what I think they were messaging towards.

The callout on "evidence" I have there is that I meant that to only be present evidence. And again, I am not convinced it can't be done. It takes a lot of work. Which, the article is doing. But just saying that traits that helped you survive are typically retained, so by definition increase fitness, does not.

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