I’ve been trying to think of a politically correct way of phrasing this question, but I think that however I say it, somebody is going to get offended.
As I understand it, the human race evolved in Africa, and the first humans were Black. As their descendants migrated around the world, they mutated and developed other racial groups, for example the settlers in Northern Europe becoming White.
Now, it seems that there are certain evolutionary disadvantages to having White skin. We English don’t get many sunny days per year, but when we do get them we tend to burn easily. This can be at least painful, or could cause serious injury. After few days in the sun we might even develop melanoma, which can be fatal. Black people, AIUI, have built-in protection, and don’t get either suntan or sunburn, and are much less prone to melanoma.
So, on the face of it, it seems that Blacks have certain evolutionary advantages over Whites, pale skinned people like me being less likely to survive to pass on the genes.
So, I presume, there must be some evolutionary advantage to White skin that outweighs the disadvantage above. Something that gives an increased chance of survival in this geographical area.
This is not true. When I go to the beach with my friends, a couple of my black guys always make sure to use suntan lotion. One of them actually burns quite easily.
Your OP seems to assume something like there is a Black Species and a White Species of humans. There isn’t, black and white people aren’t two different species competing for survival. We’re all one species that have different traits adapted for different environments.
The absorption of Vitamin D via sunlight. Darker skin can make this most difficult in less sunny climates. The result is rickets…
Of course with vitamins/sunscreen/migration these days, lighter/darker skin is of lesser and lesser value.
BTW: wasn’t there a recent study that kids are beginning to show an increase in Vitamin D deficency due to the crappy food they’re eating and lack of milk? Are these kids non-white?
Colibri answered your question, but I just wanted to add that there is nothing PC about this issue. It’s been well understood in terms of Vitamin-D for a long, long time.
We assume the first H. sapiens that appeared in Africa some 150k yrs ago had black skin, and that’s a pretty reasonable assumption, but not necessarily true. It’s possible that our early ancestor had brown skin (like you see on the !Kung San people today) rather than the dark black skin of other modern African populations.
I just want to slip in that a reduction in skin cancer is not the only reason that dark skin is selected for in sunnier regions. The UV rays in sunlight also break down folic acid, which is very important for good health. I would say that maintaining folate levels is a far stronger evolutionary pressure than the chance of melanoma.
Where does he assume this? Admittedly, the OP mentioned evolutionary advantages, but evolutionary principles don’t have to involve different species. Actually, if I remember my Darwin correctly… (not that darwin is the last word on evolution theories, just the first word, but IIRC this hasn’t changed,) it all starts in a situation very similar to what was described. A single species. A difference in traits that seems to correspond to a difference in environments.
Differentiation of species, I think, takes place after there are a number of different traits that have developed to adapt to the different environments, to such an extent that the DNA patterns are no longer quite compatible and interbreeding is impossible. Obviously that has never happened with humans, and is unlikely to in the forseeable future since modern technology is making world travel and interbreeding more common and easier. But that doesn’t mean that evolutionary processes aren’t relevant for humans.
Of course it’s a huge and completely unsubstantiated assumption that the first humans were black. There are three schools of thought, and none of them more scientifically valid than any of the others.
One says that black skin evolved in Homo erectus a result of hair loss, and so the first humans were black.
Another says that the first hominids remained white just as many chimpanzees are, and humans only became white after H. sapiens stopped living in the gallery forests during the day and foraging on the savannas at dawn ad dusk. It was only sapiens that was a true savanna animal and so only modern humans evolved black skin.
Another theory says that the fist humans al had the brown skin with aggragated melanocytes seen in the Khoi san and similar presumed primitive people today. It was only relatively recently that people evolved away fom this, in the last 70, 000 years or so. The first non-brown people may have been either black or wite, but one colour derived form the other and both were preceeded by brown.
Not that any of that changes the general thrust of the question, which is why human skin colours evolved, but it’s worth noting thatthere is no good reason to beliueve the first people were black.
Another factor that needs to be considered when discussing skin cloour is that melanin is a reasonably powerful antimicrobial, it inhibits microbial growth as well as protecting from sunlight. It is possible that black skin evolved at least in part in response to humid conditions in an effort to protect from skin infections, so people may nothave become black until they moved into more humid environments than those in which we evolved.
AIUI two types of animal are the same species if they can mate and produce offspring which are themselves capable of producing offspring. Thus a donkey and a horse are different species, because if they mate they will produce a mule, which is sterile.
As I recently mentioned in this thread (and which I end up posting in every thread having to do with speciation), this is incorrect. Many species (not just birds) are capable of producing fully fertile hybrids with other species. The essence of the Biological Species Concept is not whether two types of organisms are capable of producing fertile hybrids, it’s whether or not they do so regularly in nature.
