Genetisists show that we all come from a single woman in Africa.
Modern people from Africa don’t have “white” skin.
So I assume that “white” skin was a later evolotionary devlopment.
My question:
What natural circumstance arose that selected “white” skin?
Is it a geographical thing? Is it a random by-product of a geographical thing?
Or is it an aesthetic feature that arose after social and cultural circumstances became more important indicators of breeding success than geography??
And BTW, when did human mating and breeding success go from geography to sociology?
I offer this question in scientific good faith only.
High amounts of pigment in the skin help to protect against sunburn and skin cancer and whatnot. This is important in tropical and desert areas where there is intense heat and sunlight. As people started migrating away from Africa, especially towards temperate and cold areas in Europe, there was no longer much of an advantage to producing this pigment. So people whose bodies did not waste as much energy producing skin pigment had an advantage, and reproduced more, leading to white skinned Europeans.
Vitamin D can enter the body when eaten in fish or the body can synthesize it when subjected to a certain amount of UV radiation in sunlight. Since the production of melanin is a cost to the body, when various persons experienced a mutation that seriously reduced melanin production, those who lived in the Northern Latitudes had a better chance of success. (Darker skin means that you need more sunlight exposure to generate Vitamin D. Lighter skin means you can get by on less sunlight. Mutations that reduced melanin in climes closer to the Equator would have harmed the individual by allowing skin burns and skin cancer, so it was only selected in regions where there was less sunlight and those people, while not needing melanin protection would need a way to absorb more UV light.)
Likely these are not adaptive changes at all. Rather, they are simply variances in genetic convergence - localized by the geography. In other words, totally random and meaningless, just like difference in language, culture and religion.
Who said that it did? The question was “where did white skin come from?” Other morphological changes could be as simple as random mutation followed by a founder effect during migration. Unlike skin pigment, I am unaware of any purported advantage to the height of the forehead. If there are advantages to the shape of the lips (as there have been purported advantages to the general shapes of noses, they would have been selected in the same fashion: some mutation tends to work well in one environment while providing a disadvantage in another environment leading to a general selection for or against depending on the environment.
Given that skin cancer mostly occurs after the reproductive years, a more important selective factor for dark skin may be protection against folate, a B-vitamin.
thanks all,
so there is an energy cost for producing melanin
so “white” skin survives because that piece of energy now goes to some other adaptive feature?
Is producing melanin really that wasteful energy-wise that not making as much is helpful in figuiring out who is going to live through the winter (when not as much Vit-D will be absorbed)?
Change in diet. Humans began becoming omnivores/carnivores instead of herbivores. Large teeth and heavily muscular jaws no longer have the advantage in survival.
I think PaulFitzroy was referring to what he perceives as “Caucasian” type features relative to those of some populations in sub-Saharan Africa. But there is no real correlation between the morphological features he mentions and skin color.
I don’t think this means we all actually came from this one woman alone, but that based on the differences in our 16S mitochondrial DNA (which comes from our mother) the convergence says that we’re all related to a single woman hundreds of thousands of years ago, but we’re also probably related to almost every other human alive at that time. It is possible there were variations in skin color at that time since a cooler climate in Africa might have forced people to cover up more.