The fur of wolf and fox populations varies dramatically across latitude. I have grey squirrels and black squirrels running around in my backyard as we speak.
Riddle me this, Dopers: I can’t quite wrap my head around something like skin color evolving.
In my understanding of evolution-- which is likely incorrect in some profoundly ignorant way, of which I will soon be disabused-- you pretty much have two routes to evolve traits:
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Random trait that directly proves advantageous for survival, i.e. smarter people survive
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Random trait that piggybacks on other traits that prove advantageous for survival, i.e. all smarter people have green eyes so green eyes survive
All things being equal, lighter skin color in the northern latitudes makes better sense than darker skin color. But given the relatively short generational time frames we’re talking about here, I have trouble envisioning the kind of evolutionary pressures required to literally kill off dark-skinned people in favor of light-skinned people (or, if you want to put a happy face on it, how light-skinned humans did better enough to survive in the north).
It’s like, some mutations are so obviously advantageous that you can see how they survived. But the “minor” stuff like skin color just strikes me as such a meaningless deal that I don’t understand how evolutionary pressures worked here.
[Ken Nordine]Flesh colored?[/KN]
But it didn’t kill off all the dark skinned people outside Africa, which is why you see the gradual lightening of skin color as you head north. There are people in India who look pretty much like your ordinary Western European except they have black skin. As black as any skin you will find in Africa.
I didn’t know that. Are there black bears that are brown, and vice versa?
Purple
There aren’t any of that color around anymore, because they were selectively eaten by the Purple People Eaters, and only the more drab-colored mutant varieties survived to become the people of today. Another example of Evolution In Action, like those white moths on the sooty trees.
Yes, black bears (Ursus americanus) can be black, brown, or blonde. Brown bears (Ursus arctos) which includes Grizzly and Kodiak can also be black, brown, or blonde. The most common colors match the names, but there’s plenty of variation.
If I were to hazard a guess, I’d say the first modern humans were more-or-less the same colour as me - light brown or bronzed.
300 years is well under thousands of years. Also, this could be explained by sexual selection. That’s especially likely in the case of Boers.
Just because extremes can be reached in only a few thousand years doesn’t mean it must happen.
Does sexual selection count as #1? If not, then it must be #3.
Secondly, sometimes things can seem to evolve very quickly simply because the possibility already existed, but the controls for it change. I suspect that Darwin’s Finches might be a good example of this: in the past, finches could have had the ability to rapidly change beak dimensions to deal with ecological changes. So, all the necessary genes to have shorter or longer beaks, or more robust or facile beaks, are in the genome, but the currently appropriate ones are more ‘switched on’ than the inappropriate ones. It’s quite possible that human skin color has changed to light and back to dark any number of times, in subsaharan Africa (but generally, only in arboreal ecologies, where the dark skin isn’t necessary.)
Likewise, melanism might have varied considerably even just in subsaharan Africa. As noted earlier, light skin is likely to be original. So, it doesn’t take a major mutation to simply mute or switch off production of melanocytes.
A more specific case is the melanism of redheads and other very fair-skinned people. Not only are there fewer melanocytes fewer, but they tend to cluster (reducing their effectiveness). So sometimes the effect of a mutation isn’t to simply increase or reduce, but to change the distribution.
Another factor is that a feature (like dark skin) can be lost simply because it’s no longer necessary. That is, as long as there is pressure to retain a feature (especially a relatively new one, or a very complex one), the genes for the feature stay frequent in the population. But as soon as the pressure goes away, the feature can fade away simply because it’s not maintained – there’s no pressure to “fix” the “broken” genes. Examples of this iinclude blind and colorless species living in dark caves or very deep ocean, where there’s no light.
Keep in mind that dark skin is the “more advanced feature” – adding melanin to the skin to absorb harmful radiation. Light skin is more or less the default, lack of a specific (and complex) feature.
Previous thread and in specific, previous post with links. Of note this link pertinent to the speed of skin color changes:
Not a chance, the dates could easily be wrong but there is zero evidence that primates or apes and hominids evolved anywhere but Africa. Even proto-primates like lemurs are found near Africa(Madagascar).
With apologies for the nitpick of a very solid post, I presume you meant “gracile” 
I think the consensus is that apes originated in Asia.
Yep - Gibbons are (AFAIK) only Asian and they’re the stem ape.
Hmm you’re right and not only apes, it appears the theory of early primates originating in Asia gaining steam.
I wonder how that date lines up with primates reaching south america 40 million years ago, from Africa.
I just learned that word yesterday before I read this post!
Great word. I also learned yesterday a cool one in botany and zoology for hairless, smooth, “nude,” which I’ve forgotten now, beginning with “gr.” Any help?
You mean glabrous.