Out of Africa, so why did the European skin change colour?

[bpesta22]

How ya been Delvo.

Have you seen this in press article

(OT here).

http://lesacreduprintemps19.files.wo...haprinderm.pdf

[CapelDodger]

Originally Posted by Explorer

The fact that my normally white skin turned a healthy brown recently, adds to the mystery. My skin has the ability to adapt to a sudden change in my environment, turns darker, and presumably gives me an added protection from further possible long term exposure.

So why did those ancient ancestors out of Africa develop that ability when moving to less sunnier climes?

You're assuming that the ability isn't present in black Africans. More or less tanned black Africans look no different in the visible spectrum, but it's the UV that matters.

We notice tanning in white people because the contrast is so great. As to it being "healthy-looking", that's just fashion - a milky-white skin was the fashion until quite recently, and only the lower classes were exposed to weather on a regular basis. Hollywood and Acapulco changed that.

[CapelDodger]

Originally Posted by epepke

The vitamin D explanation was popular for a while, but about 20 years ago it was discovered that with just face and arms exposure for 15 minutes a day, it is still possible for a very dark person to get enough vitamin D. Still, it's controversial. It's possible that pregnant women didn't get enough. There are also some bone diseases in the skull record, but those may be more due to lack of nutrition.

The current thinking is that it's because white skin seems to be more resistant to frostbite.

When cold is a problem, clothes are the obvious response, not 15 mins of arm exposure every day (which would, lets face it, be counter-intuitive). That current of thinking isn't carrying me along at all, I'm afraid.

[Vermonter]

Originally Posted by Marduk

The gene responsible is called SLC24A5,
http://en.wikipedia.org/wiki/SLC24A5
it was only discovered failrly recently, and its effects on human populations have been timed to around 5,300 to 6,000 years ago, which means of course that there were no white people around at all prior to 4000bce, you might want to go and take a look at those figures in cave paintings at this point, there's a reason they were drawn with brown pigment.

Just wanted to say that I learned something today! I did not know that, thank you for posting it.

[Toontown]

You can bet your bottom dollar that melanin stopped being survival selective. Think really hard about why that happened.

Can't figure it out? Obviously, the lighter pigmented people were the original "spooks". No kidding. The darker people thought they were ghosts. When the lighties realized the darkies were scared of them, they chased all the darkies away. It didn't take a darkie long to look at a spook. They beat feet back to Africa.

Later, the Celts learned to take advantage of the pigmentation phobia by painting themselves blue, which was hair-raisingly frightening. Plus, the Celts were mean as hell. Not particularly good fighters, just nuts, and real scary.

So it was that genes learned that, in Europe, skin pigmentation was at best unnecessary. Success was mostly a matter of what color was the scariest, which turned out to be blue, which could be painted on.

So there you go. Nature's way. Use it or lose it.

[paiute]

Originally Posted by Explorer

Having spent the last two weeks in Turkey, and developing a healthy looking deep tan on my usually pale white skin, it begged the question as to why homo-sapien skin lost the permanence of black pigmentation presumably naturally selected for the powerful and potentially damaging sun of Africa, from where some of our ancestors emigrated.

http://en.wikipedia.org/wiki/Begging_the_question

[Delvo]

Originally Posted by bpesta22

Wouldn't you only lose them if they cost something? Would neutral traits not be selected for or against?

A lack of selection one way or the other can still result in loss of a feature just because the mutation rate doesn't change and there's nothing to prevent any particular mutation from spreading.

[Hans]

One other possibility is that HSS got the 'white' gene from the Neanderthals who had been in the north for hundreds of thousands of years. Since we contain their genes this is a possibilty

[bpesta22]

Originally Posted by Delvo

A lack of selection one way or the other can still result in loss of a feature just because the mutation rate doesn't change and there's nothing to prevent any particular mutation from spreading.

Can it therefore also result in an increased frequency of the feature?

[Robrob]

Originally Posted by Toontown

You can bet your bottom dollar that melanin stopped being survival selective. Think really hard about why that happened.

Can't figure it out? Obviously, the lighter pigmented people were the original "spooks". No kidding. The darker people thought they were ghosts. When the lighties realized the darkies were scared of them, they chased all the darkies away. It didn't take a darkie long to look at a spook. They beat feet back to Africa.

Later, the Celts learned to take advantage of the pigmentation phobia by painting themselves blue, which was hair-raisingly frightening. Plus, the Celts were mean as hell. Not particularly good fighters, just nuts, and real scary.

So it was that genes learned that, in Europe, skin pigmentation was at best unnecessary. Success was mostly a matter of what color was the scariest, which turned out to be blue, which could be painted on.

So there you go. Nature's way. Use it or lose it.

Wow, that's pretty good. You sound almost exactly like a racist nutjob!

[Beelzebuddy]

Originally Posted by Robrob

Wow, that's pretty good. You sound almost exactly like a racist nutjob!

I was wondering when we'd start edging over this particular line. My money was on Whitey blending in with the snow.

[Explorer]

Originally Posted by paiute

http://en.wikipedia.org/wiki/Begging_the_question

...and your point is?

[Craig B]

Originally Posted by Toontown

You can bet your bottom dollar that melanin stopped being survival selective. Think really hard about why that happened.

Can't figure it out? Obviously, the lighter pigmented people were the original "spooks". No kidding. The darker people thought they were ghosts. When the lighties realized the darkies were scared of them, they chased all the darkies away. It didn't take a darkie long to look at a spook. They beat feet back to Africa.

Thank you for that most informative post, which has helped me to understand the philosophy underlying your many interesting contributions to these threads.

[Craig B]

As regards climate induced loss of melanin, it has been pointed out that native Tasmanians lived in a relatively cool and rainy environment, and that their ancestors had been there about as long as Europe has been inhabited, but they remained dark skinned. This would tend to support the sexual selection theory, which has also been invoked to account for the variation in hair coloration in Europe.

[pakeha]

^
Good point about the Tasmanians.

Originally Posted by Hans

One other possibility is that HSS got the 'white' gene from the Neanderthals who had been in the north for hundreds of thousands of years. Since we contain their genes this is a possibilty

It is a fact that Africans do not have Neanderthal genes, correct me if I'm wrong.

[Delvo]

A couple of other things I forgot to mention before: exposure to sunlight doesn't only lead to production of vitamin D, but it also destroys vitamin C. And there's been some evidence that skin permeability is higher in light skin and lower in dark skin. But not much is known yet about when & where each of these matters in natural selection.

Originally Posted by Hans

One other possibility is that HSS got the 'white' gene from the Neanderthals who had been in the north for hundreds of thousands of years.

Because mutations which make no difference in a gene's effects occur at a predictable rate, geneticists can measure how long a particular type has been around to collect mutations by checking how many mutations there are. All light-skin genes I've heard of have been dated to a time too recent to have come from Neandertals. I have not seen any reports of what effects the genes that seem to have come from Neandertals have in modern populations, which makes me suspect they're all still of unknown function (as most genes still are!), because if any of them had known functions, that probably would have been reported because it would have interested readers. (I'm sure that when most people read that Neandertal genes are still around, the next thing they thought was "What do those genes do?".) So it seems that the genes behind our current skin colors and the Neandertal genes that are still around are two different groups of genes, not overlapping.

Originally Posted by bpesta22

Can it therefore also result in an increased frequency of the feature?

It's possible but practically never happens because the number of possible mutations that would make a feature not work/develop anymore far outnumbers the number that would have any effect that could be called an improvement.

Of course, the real trouble with neutral selection is that we can't really be sure of examples to point out, because there could be costs or benefits for almost any trait that we just don't know about yet.

[Damien Evans]

Originally Posted by Craig B

As regards climate induced loss of melanin, it has been pointed out that native Tasmanians lived in a relatively cool and rainy environment, and that their ancestors had been there about as long as Europe has been inhabited, but they remained dark skinned. This would tend to support the sexual selection theory, which has also been invoked to account for the variation in hair coloration in Europe.

Much lighter skinned than Anangu (The people native to the Alice Springs region) are though.

[Toontown]

Originally Posted by Craig B

Thank you for that most informative post, which has helped me to understand the philosophy underlying your many interesting contributions to these threads.

Somehow, I doubt that. I suspect that you are once again grasping at the straws of my "underlying philosophy".

[trebor]

Originally Posted by bpesta22

Wouldn't you only lose them if they cost something? Would neutral traits not be selected for or against?

You could indeed lose them, see for example Vitamin C production in people.
We still have the gene for it but it is no longer functional.

[Sideroxylon]

This TED Talks lecture on the subject is worth a watch.

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I AGREE

[Explorer]

Originally Posted by Sideroxylon

This TED Talks lecture on the subject is worth a watch.

YouTube Video This video is not hosted by the JREF. The JREF can not be held responsible for the suitability or legality of this material. By clicking the link below you agree to view content from an external website.

I AGREE

Yes very good, and an eloquent speaker.

In one of the slides, she shows Neanderthals unclothed, and used as an example of how lower melanin levels would be selected in European lower levels of uvb radiation, essential for Vitamin D etc. Is the speaker asserting that in a much colder climate, Neanderthals (and homo-sapiens by implication) would have been naked? Surely they would have covered up in the colder climate, shielding much of the benefit of available uvb radiation to the skin.

[Damien Evans]

Originally Posted by Explorer

Yes very good, and an eloquent speaker.

In one of the slides, she shows Neanderthals unclothed, and used as an example of how lower melanin levels would be selected in European lower levels of uvb radiation, essential for Vitamin D etc. Is the speaker asserting that in a much colder climate, Neanderthals (and homo-sapiens by implication) would have been naked? Surely they would have covered up in the colder climate, shielding much of the benefit of available uvb radiation to the skin.

Actually, there's even more benefit if you cover up, because while you get less hitting your skin overall you still get adequate amounts if you're light skinned, while you get all sorts of problems if you're not.

[Craig B]

Originally Posted by Toontown

Somehow, I doubt that. I suspect that you are once again grasping at the straws of my "underlying philosophy".

Even if I was drowning I wouldn't touch these straws with a barge pole.

[Craig B]

Originally Posted by Damien Evans

Much lighter skinned than Anangu (The people native to the Alice Springs region) are though.

That's interesting. It raises the question of how long it took for Europeans to become depleted in melanin. This process was not far advanced in Tasmania, but absolutely complete in Ireland. Yet Ireland was settled very much more recently than Tasmania. How long did it take the latter population to become so white skinned?

[Tatyana]

Originally Posted by Craig B

As regards climate induced loss of melanin, it has been pointed out that native Tasmanians lived in a relatively cool and rainy environment, and that their ancestors had been there about as long as Europe has been inhabited, but they remained dark skinned. This would tend to support the sexual selection theory, which has also been invoked to account for the variation in hair coloration in Europe.

It does appear that Tasmania still receives a significant amount of UVB, so the vitamin D hypothesis is still plausible.

There is also the whole albinism hypothesis, however, I haven't found a link yet that does not appear somewhat biased.

[Cainkane1]

Incidentally a tan isn't healthy. A tan is a reaction to injury and can cause skin cancer.

[Damien Evans]

Originally Posted by Craig B

That's interesting. It raises the question of how long it took for Europeans to become depleted in melanin. This process was not far advanced in Tasmania, but absolutely complete in Ireland. Yet Ireland was settled very much more recently than Tasmania. How long did it take the latter population to become so white skinned?

Tasmania is 10 degrees closer to the equator than Ireland though and the Southern Hemisphere tends to get more UV Rays than the Northern on average IIRC.

[Craig B]

Originally Posted by Damien Evans

Tasmania is 10 degrees closer to the equator than Ireland though and the Southern Hemisphere tends to get more UV Rays than the Northern on average IIRC.

Yes I can see that from Tatyana's map at #65. I didn't know that before. I thought insolation was more symmetrical.

[JonathanMaxBerman]

http://www.nature.com/jid/journal/v1...d2011358a.html

This is a good review on what we actually know on the topic.

[Piscivore]

Originally Posted by Delvo

Lighter skin... makes shapes/contours easier to see, which improves people's ability to spot each other, recognize & identify each other...

Wait wait wait- did you just say black people all look alike?

[WildCat]

Originally Posted by Explorer

Having spent the last two weeks in Turkey, and developing a healthy looking deep tan on my usually pale white skin, it begged the question as to why homo-sapien skin lost the permanence of black pigmentation presumably naturally selected for the powerful and potentially damaging sun of Africa, from where some of our ancestors emigrated.

I wouldn't presume the humans that migrated out of Africa had black skin, like you see in modern West Africans. Remember, Africans have been evolving this entire time too and IIRC the darker-skinned Bantu people appear relatively recently in the record. Older groups like the San are lighter skinned.

[Explorer]

Originally Posted by WildCat

I wouldn't presume the humans that migrated out of Africa had black skin, like you see in modern West Africans. Remember, Africans have been evolving this entire time too and IIRC the darker-skinned Bantu people appear relatively recently in the record. Older groups like the San are lighter skinned.

There are surely bound to be degress of darkness of pigmentation in populations evolved within areas near the Equator and the tropics. Northern Europeans however, have a fairly uniform paleness, so this is the comparison that is the essence of my original question.

[shadron]

"Why are Europeans White?"

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I AGREE

[Craig B]

Originally Posted by Explorer

There are surely bound to be degress of darkness of pigmentation in populations evolved within areas near the Equator and the tropics. Northern Europeans however, have a fairly uniform paleness, so this is the comparison that is the essence of my original question.

Is the variation in European hair and eye pigmentation likely to result from the same processes that gave rise to changes in skin colour?

[Travis]

I thought that the skin color change happened when the tribes were still largely concentrated in the Levant. Was that just an older hypothesis undone by new genetic analysis?

[MRC_Hans]

Originally Posted by Explorer

I can understand that a "white" mutant gene in our ancient ancestors would no longer be de-selected in a European climate, but why a total loss of the "African" gene? A total loss would surely only occur in the event of an adverse environmental effect, like the Vitamin D problem for black skin, cited above.

Really, reading posts till now, I think your question has been adequately answered. Why do you keep asking?

1) Unused traits tend to disappear (because ultimately, any trait has some kind of cost).

2) Vitamin D.

What more do you want?

Hans

[nota]

so why do we have white/lite people in egypt 4000 BCE

[Sideroxylon]

Originally Posted by nota

so why do we have white/lite people in egypt 4000 BCE

How light were the people there 4000BCE and how do we know it? Putting that question aside, the fact that Egypt is on the Mediterranean means that there has been much more contact and settlement by Europeans. As there has been with the entire north African coast.

[Explorer]

Originally Posted by MRC_Hans

Really, reading posts till now, I think your question has been adequately answered. Why do you keep asking?

1) Unused traits tend to disappear (because ultimately, any trait has some kind of cost).

2) Vitamin D.

What more do you want?

Hans

I note that you have quoted post 9. Since then there have been a further 69 posts. Having like you, read those 69 responses I am fairly happy, but still not totally convinced, due to some of the diversity of opinion between other posters, particularly concerning the Vitamin D theory. But ho hum and sorry if I have upset you as a consequence.

[Beerina]

Originally Posted by GlennB

To enable vitamin D production in the skin in those less sunny northern climes?

This assumes a more complicated DNA issue requires disadvantageous pressures to disappear.

Merely being complex suggests random rescrambling of sexual reproduction, to say nothing of real mutations, could disable the feature, and without the evolutionary pressures to weed that out, it just disappears.

A structure is not of equal weight to not having it, all other things being equal. One need not have evolutionary pressure at all to get rid of it -- just normal randomization or mutational processes will disable it, and that will spread sans preasure to do away with the new, disabled feature.