see hed. Means: I know they’re not (they look Eskimo-ish). But:
Isn’t having dark skin inefficient for heat regulation?
Now, I’m clever, and I point out that Africans, who started the whole Homo sapiens thing, live in a hot land, and are also…dark to man-that’s-dark skin.
Out of Africa latitudes, you get less sunshine and still need your Vitamin D, so evolution decided the trade off was worth it as long as we figured out clothes?
Selection factors “decide,” evolution happens.
Yes, vitamin D absorption is important. Physical adaptations for temperature come other ways, like body shape.
People whose ancestors lived where there’s a lot of sunlight have dark skin. People whose ancestors lived where there’s not much sunlight have light skin. Eskimos are just one more example of this general rule.
It’s not just sunlight. It’s a tradeoff between the skin-cancer protection offered by melanin and the ability of Vitamin D to extract calcium from dairy products offered by light skin.
The traditional Inuit diet contains a lot of red meat which contains vitamin D. The only populations that experienced a selection pressure towards white skin are those that a) live at high latitudes and b) don’t receive enough vitamin D from their diet: ie, agricultural people.
Look at a map of where all of the agricultural societies formed. They are all low-latitude societies: Mesoamerica, sub-Saharan africa, the Fertile Crescent, the Indus Valley, New Guinea, and the Yellow River. The only exception to this rule is the agricultural society that grew up in Northern Europe, where the Gulf Stream’s effects allowed early agriculture at much higher latitudes than normal. It’s no coincidence that pale skin evolved around the Baltic Sea.
Why would they have dark skin? Their ancestors are from North-East Asia, where people have light skin. As for V-D, many types of fish are a good source, and fish have traditionally been an important part of the diet of polar peoples.
I read your question as “why ARE Eskimos are black-skinned people?”
That calls them “bronze.” They’re certainly darker than northern Europeans, much lighter than equatorial Africans. Clearly their very ancient ancestors were among the several emigrant groups that lost substantial amounts of their melanin; but, selection pressure for lighter skin has not been strong enough to take it as far as elsewhere in the world.
because Uncle Ben or Aunt Jemima on the Eskimo Pie wrapper wouldn’t look right.
An interesting link. Nina Jablonski expands here.
According to Jablonski (who is consider the expert) the main selection factor (pigmenting to protect its levels) is folate and then vitamin D (depigmenting to increase it).
The difference being the retention of the ability to tan, which is useful even in the high Arctic, because it protects against UV exposure and doesn’t interfere with vitamin D and folate levels in a meat-eating population. Sunlight creates vitamin D, and destroys folic acid.) There is a heavy selection pressure towards regulation of these vitamins because deficiencies in both cause serious birth defects. Switching to a grain-based diet means no dietary sources of vitamin D (but grains are dietary sources of folic acid), so any child of a Scandinavian neolithic mother who retains the tanning gene is much more likely to be born with birth defects.
Cancer protection is not an evolutionary determinant. Skin cancer usually happens at an age when people are not reproducing anymore.
But UV light destroys folate, that is one of the forms of vitamin B. Deficiency in folate happens in children, so has evolutionary consequence.
And the position of the tradeoff point is determined by the amount of sunlight.
If personal reproduction were all that mattered evolutionarily, then humans wouldn’t live past reproductive age to begin with. But humans can help spread their genes even long after they’re done personally reproducing (by passing on their wisdom to their descendants), so things which cause death in old age are still relevant, just not as much so as things that kill quicker.
But people that get skin cancer and die of it are usually still able to pass on their genes, so of course those genes that predispose people to skin cancers are still going to be in the population at large. On edit I reread your post and I think I get what you’re saying, but I guess in the not too distant past it didn’t matter as much because it wasn’t that long ago that many people didn’t live past their 30’s.
The source of dietary calcium is just as important.
Any dark-skinned Eskimos would be prime targets of polar bears.
Darwin wins.
See this : https://www.youtube.com/watch?v=X3eUP4-BlXI for a summary of this theory. Based solely on latitude, you would expect that Eskimos and Mongols would be the same color as Scandinavians and Scots. But obviously Scandinavians and Scots are noticeably paler than Eskimos and Mongols, on average. The reason is that Scandinavians and Scots have spent thousands of years as agricultural societies based around the growing of grain, which doesn’t give a lot of Vitamin D. Mongols and Eskimos have predominantly been hunting peoples who get lots of Vitamin D from meat.
Also, keep in mind that light skin evolved (at least) twice in our lineage as a species. The mutation(s) that led to light skin in Europeans are not the same as the one(s) that led to same in East Asians. So, one needn’t expect light skinned Asians to have the same skin hue as light skinned Europeans.
This is mostly a fallacy. It’s true that for most of history, the life expectancy of the average human was somewhere between 30 and 40. It’s not true that thirtysomethings were just dropping dead all over the place all the time. The big issue was that infant mortality was enormously high. Just making it to age 5 was uncommon - most children died. But if you got to age 20, your odds of making it to 50 or 60 wasn’t that much lower than it is today. That’s also one of the reasons that people in the past had many more children than is common today - because half of them died and they finally ended up with a family more along the lines of today! This was the rule up until very recently, perhaps WW1 era. One of my ancestors who was a westward pioneer in the “old west” had about five children. Only two lived beyond age 10 - my more recent ancestor, and one other kid. That was just life as usual. That was also one of the reasons behind having such (by our standards) early ages for marriage - because people needed plenty of time to get pregnant a dozen times so that they could end up with a few living children to support them later in life.
Perhaps your odds of making it to ~50 were, but not 60. Not unless you were in the upper class.
We (the industrialized world) are barely at replacement level today, so that (the bolded part) is obviously not true given the rapid increase in population of the last few centuries.