Evolution is survival of the fittest. That's not a tautology, it actually says something, namely that the traits which survive and thus propagate tend to be the ones that enable some form of adaptation to its living conditions to the individual. The paper lists a bunch of examples:
- lactose tolerance
- immunity and disease resistance
- lighter skin at northern latitudes
- metabolism and vitamin D processing changes in response to changes in diet after the rise of agriculture
All these traits go beyond just increasing the odds of survival, they improve the life of the individual directly. I.e. they confer fitness. Individuals carrying those traits will, on average, in that ecosystem they are inhabiting, be more healthy than those who don't.
It's more reproducing than surviving. If the population of some species increases and the number of copies of some allele remains constant we could consider than gene less fit than the other alleles, in the population genetics sense. So it's frequency rather than survival that geneticists look at. But that proves that there are indeed other ways that they could have defined fitness if they wanted to.
Well that's a given mate, nobody's talking about populations that dont reproduce are they? And even then you're still making the same tautological mistake.... If they survived they must have been fit
The flip side is everything is being degraded by random mutation.
It's like holding a large ball in place on a hill that sees frequent tremors. If the ball is still halfway up the hill it's being held in place, if it's being held in place it's still halfway up the hill. It might be considered a tautology if you're only working with symbols and ignore all the mechanistics.
Remember, all improvements are changes, but most changes aren't improvements. The trick that makes evolution works is this: out of lots of random changes, most of which are harmful, the harmful ones tend to be weeded out and the useful ones tend to spread.
Whatever does not survive stops registering in later times; most of the time, what helps survival is retained, and what helps survival is what increases fitness.
As stated, this feels wrong. Specifically, it does not account for traits being appropriate for environment. I like to say it as what was needed for one stage could be the problem for the next stage.
That is, traits that stop registering may no longer be something that helps survival. But that does not mean they were not necessary for survival at an earlier point.
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.
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.
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.