Posted: Apr 09, 2018 6:43 pm
Sendraks wrote:The_Piper wrote:Papa Smurf wrote:Sendraks wrote:Take a load of white europeans to Africa, ensure that they live mostly outdoors (rather than in nicely air conditioned houses) and within a few generations their offspring will be noticeably darker skinned.
Seems to me that would only be true if dark skin would be selected for by those with lighter skin dying of skin cancer. If sunscreen gets used properly (or more in general if medical care keeps them alive until after they have reproduced) they would stay white as lilies
Or is it possible that extensive exposure to sun activates previously inactive genes in an individual and this gets passed on genetically through sperm?
I think the lighter/darker skin color difference has to do with vitamin d uptake. Lighter skin absorbs more. Maybe taking vitamin d capsules negates that selection pressure now. My point about our distantly future generations surely evolving into a different order of mammals might also be negated by man-made factors.
Papa makes a fair point, it is unlikely to be just a few generations but, I think I read something a while back about melanin production in humans and it being much more adaptable. However, I can't find the source to back it up, soooo its probably a wash.
What I do know is that the process of evolving from paleskinned hairy apes living in forests to dark skinned hominids out on the savannah, was a process of change over millions of years. Whilst the change from dark skinned hominids to pale skinned europeans, took only a couple of hundred thousand years. And there is some genetic research around how the genes controlling melanin production are more responsive to changes in circumstances.
My reply meant to point out that it's absorption of vitamin d, not skin cancer, which is the more important factor in skin color afaik (I may be half wrong). I don't disagree with his point about sunscreen.
From the Wiki article - https://en.wikipedia.org/wiki/Human_skin_color#Sexual_dimorphism
Adequate vitamin D resources are needed to absorb calcium from the diet, and it has been shown that deficiencies of vitamin D and calcium increase the likelihood of various birth defects such as spina bifida and rickets. Natural selection has led to females with lighter skin than males in all indigenous populations because women must get enough vitamin D and calcium to support the development of fetus and nursing infant and to maintain their own health.[7]
According to that Wiki article, light skin in southern Europe may be a recent thing, only within the last 8000 years or so.
"The SLC24A5 variant spread very rapidly throughout central and southern Europe from about 8,000 years ago, whereas the light skin variant of SLC45A2 spread throughout Europe after 5,800 years ago."
https://en.wikipedia.org/wiki/Human_skin_color#Europe