One of the dynamics which is always operative in evolutionary biology is adaptation through natural selection. We know that it happens in humans, and it is clear that it has happened in the past and is happening in the present. It’s most obvious when it comes to disease. You can see the spread of malaria adaptations in the New World, for example, and that’s clearly due to strong natural selection.
But it’s not just disease. A few years ago I noticed that ancient DNA was detecting evidence of rather recent depigmentation across Northern Europe. This is not to say that the general features of the phenotype in Northern Europeans were not mostly there by the Bronze Age. The Beaker People in Britain don’t seem that much different from modern British people.
Nevertheless, using the genomic resources now available to us, a few years ago researchers developed methods looking deep in the genome and found evidence of selection in English populations over the last few thousand years. One of those characteristics was pigmentation. Using similar methods, the Estonian group has found something similar, Differences in local population history at the finest level: the case of the Estonian population, has found something similar:
Another SNP from this list, rs7114857, lies within the GRM5 gene which has been shown previously to be a potential target of natural selection for the pigmentation phenotype [28]. See Supplementary text 5.4 for details.
If you look at my post above, it’s pretty clear Baltic populations were pretty fair-skinned 3,000 years ago. But, these are the fairest populations in the world. And, it looks like that both ancient DNA and “best-of-breed” selection detection methods like SDS are pointing to further allele frequency shifts on the margin.
The question is why? First, there are two issues
– Pigmentation alleles can be pleiotropic. Pigmentation may not be the target of selection.
– If it is the target, then the debate moves to sexual and natural selection.
Pigmentation is an easy trait to discern. There is surely lots of selection in and around disease. But what other traits? The paper points to bone density is one characteristic, and size seems to go up and down a lot.
It’s sad George Williams wasn’t around to see the 21st century renaissance of “adaptationism.”
As we’re seeing during COVID figures of apparent high incidence in UK of non white deaths (not sure if that stat proved accurate in the end?), vitamin D deficiency has also been shown to be very high among the dead in other studies. At high latitudes pale skin must be very important. Vitamin D supplements are recommended by NHS for all newborns in UK, and in Scotland during winter there is only a few hours of sunlight, high melanin simply does not absorb enough for many months of the year. The selection pressure is likely very powerful over even short time periods due the rapid debilitations associated. This lack of VitD may be compounded by cultural diets not high in dairy due to lactose intolerance.
Is she a faux blonde? See the color at the parting of her hair.
@A. Karhukainen – blonde hair gets blonder when exposed to the sun. So the longer parts of the hair will be blonder than the hair at the root. I know someone who is very blonde who at the root is quite dark.
Adaptationism is obviously the thing. The fact that lots of biologists have been averse to it says something about biologists, something bad.
After spending some time in Northern Europe, I became more convinced of the old explanation for depigmentation in that place (the need for sun-driven vitamin D synthesis). The sunshine there is so weak that even in summer you can barely feel it.
So what exactly is the argument that preference for “whiteness” can’t be driving the process?
sexual selection is almost always deus ex machina in humans (sorry darwin).
but u can believe whatever you want. i don’t care
but u can believe whatever you want
Thanks, I will. I don’t have a “belief” one way or the other. The science is above my paygrade. I just notice that people who seem knowledgeable in the field seem to go out of their way to always say that preference for skin color can’t possibly be the driving force and I wonder how they can know this.
sexual selection is put in the discussion of every single paper. no one knows. who are you talking about? who is “that people” besides me and greg?
there are some prior reasons to think humans are not highly sexually selected. but who knows?
– If it is the target, then the debate moves to sexual and natural selection.
Thanks. I re-read related posts and some related posts of related posts, and combined with a greater appreciation for the if in the above sentence I have a better understanding.