Is there any way to know what color skin the first Homo Sapiens had? How long did humans exist before major variations in skin color appeared? Is the variation in skin color among different people due to environmental pressures and selection, or just random genetic mutations that stuck because they weren’t harmful?
To me, it seems that humans vary in superficial characteristics (like skin, body size/height, and hair color) more than most other species. The only other species I can think of with such a wide variety of superficial characteristics are dogs, house cats, and horses, all which humans have deliberately bred superficial characteristics for.
From Wikipedia:
“Variation in natural skin color is mainly due to genetics, although the evolutionary causes are not completely certain.”
“It is theorized that about 1.5 million years ago, the earth endured a megadrought that drove hominids from lush rainforests into arid, open landscapes. This, coupled with the loss of dense body hair, caused early human skin to endure excess UV-B radiation and xeric stress.[43] Rogers et al. (2004) performed an examination of the variation in MC1R nucleotide sequences for people of different ancestry and compared the sequences of chimpanzees and humans from various regions of the Earth. Rogers concluded that roughly five million years ago, at the time of the evolutionary separation of chimpanzees and humans, the common ancestors of all humans had light skin that was covered by dark hair. Additionally, our closest extant relative, the chimpanzee, has light skin covered by thick body hair.[44] Over time human hair disappeared to allow better heat dissipation through sweating[3] and the skin tone grew darker to increase the epidermal permeability barrier[43] and protect from folate depletion due to the increased exposure to sunlight.[4] By 1.2 million years ago, around the time of homo ergaster and homo erectus, the ancestors of all people living today had exactly the same receptor protein as modern Africans.[44] Evolutionary pressure meant that any gene variations that resulted in lighter skin were less likely to survive under the intense African sun, and human skin remained dark for the next 1.1 million years.”
As outlined above, from the time humans lost most of their body hair until they left the equatorial regions of Africa, they almost certainly had very dark skin, like populations living in that part of the world today.
However, dark skin blocks the production of vitamin D in the skin. Paler skin tones evolved once humans migrated into temperate and subarctic areas in response to lower levels of sunlight. Today there is a correlation between pigmentation and latitude in native human populations. (There is some lag in the evolutionary response to this factor. In the Americas equatorial populations are darker than Arctic ones, but the gradient is not nearly as great as in the Old World, where there has been more time available for differences to develop.) The palest populations are found in Northern Europe, which not only receives less sunlight but also has a cloudy, rainy climate.
While hominids have been around a bit, what we would call “humans” are thought to have been around only a couple hundred thousand years. For humans who think and behave like us, it might be a lot less than that.
We probably didn’t manage to sneak out of africa until 50,000 years ago, and maybe not into the northern latitudes until 20 or 30,000 years ago, (most likely in more than one migration event) so I think the answer to your “how long” question is that we all started dark-skinned and stayed that way for 150,000 years. The ones that got pasty white probably didn’t show up until 30,000 years or so ago at the earliest.
All round numbers, and I’m not an anthropologist so this is the armchair shorthand.
Trying to remember where I read this, but one author posited
a) Melanism changes quite rapidly in humans, taking only a few thousand years to change between extremes
b) There is evidence that sexual selection might have been at play among arboreal peoples in subsaharan Africa, since dark skin is not naturally advantageous in forests, yet there’s evidence that certain peoples inhabited these regions continuosly for a long enough time to lose the dark pigment. Some of these peoples are among the darkest-skinned.
The gene that causes white skin in Europeans suggests that it appeared roughly 10,000 years ago, and maybe as recently as 6,000 years ago. Since this coincides with the rise of agriculture, it has led to a theory that eating less meat and fish as sources of Vitamin D made it necessary to absorb more UV radiation through the skin. Bottom line is that we don’t know for sure yet exactly why or when white skin came about, but I might have to alter the mental image I have of the European cave painters as white-skinned.
This is a popular theory, but anthropologist Peter Frost explains here why the skin color/vitamin D story is full of holes and why the more likely explanation for light skin color in Caucasians is sexual selection:
Recent findings of Asian human bones show that modern humans had colonised Asia at least 50,000 years ago. This means that evolution time to go from alleged African origins to Asian has become incredibly small - and implausible.
Does anyone continue to believe we made the astonishingly rapid physical transition from African to Asian and Caucasian form in just tens of thousands of years? Or, as it appears increasingly likely, we are human beings with distinct and separate racial origins?
The day when human remains are found to be older than those in Africa is the day the ‘Out of Africa’ theory collapses. This latest find takes us ever closer to that day.
It’s not “increasingly likely”, it’s pretty much impossible. There just are not the kind of consistent genetic differences you’d get from separate origins; the “races” are not genetically coherent groupings. It’s not “astonishingly rapid” either when you consider how much faster wildly different looking dog breeds can be bred.
Yes. It remains the majority view as far as I know. It’s not an ironclad hypothesis but it has the strongest archaeological and genetic evidence to date. Again AFAIK, I’d welcome correction.
There are a couple of competing hypotheses, but even the ‘Regional Continuity’ hypothesis assumes gene flow between world populations which prevented reproductive isolation and it still is ultimately “out of Africa” if you go back far enough in that it assumes archaic human populations arose from Homo erectus, which still originated in Africa as far as anyone can tell.
The ‘Assimilation/Partial Replacement’ hypothesis argues for a synthesis. Modern humans originated in Africa and migrated out as per ‘Out of Africa’, which fits the best data to date. But they then encountered, interbred and absorbed in situ archaic human populations, which may explain some of the arguable holes in the OoA hypothesis.
Thank you for your responses. Mosier desperately informs me that humans absolutely did not evolve simultaneously… I did not say they did evolve simultaneously - I said separately.
Tamerlane on the other hand gives a more cautious and qualified reply, and leaves the door open for further evidence either way.
However, you all ignore the irrefutable conclusion from a recent find of an anatomically-modern human skull in a cave in Laos, dated between 46,000 and 63,000 years old. The dated find erodes the time for alleged physical transition from African to Asian and Caucasian form. It makes the ‘Out of Africa’ theory less plausible.
It is reasonable that, eventually, further anatomically-modern human remains will be found, older than those in Africa, and the ‘Out of Africa’ theory will collapse.
Unless you are positing different populations traveling through time differently, “separately” also perforce means “simultaneously.”
Or it moves the exodus from Africa earlier. Which is more plausible – evolution of different creatures into the one homogenous species we have today, or that we missed something in the known-to-be-sparse fossil record showing an earlier migration out of Africa? Hint: it’s the latter, by a mile.
I think you are confusing two things. Those dates are perfectly compatible with the OoA theory (not going to call it a hypothesis because it is fully tested) but you are assuming the person to whom the skill belonged would look “Asian”. We don’t know what skin color he or she would have had or whether or not the person’s eyes would have epicanthic folds or not.
The thing is, if you look at certain population of Africans (in particular, the San Bushmen), you can see traits that are associated with lots of non-African populations.
There is no reason that modern humans could not evolve into the different populations we see today in the timeframe given in the OoA theory. And it should come as no surprise that those OoA humans could and did interbreed with other extant populations once they left Africa, although the amount of genetic material remaining today from such matings is quite small.