How Europeans evolved white skin

[Jomid59]

So what you are saying is that if an African drinks a lot of milk his skin will become white.

Maybe we will find out....

"one uncontested truth is the demand for milk is growing across the continent. A recent survey published by global packaging company Tetra Pak is projecting Africa to see an increase of more than 50 percent in liquid dairy consumption"
http://www.africa.com/blog/dairy-con...africa-part-1/

[1798]

Vitamin D is in milk.

Lactose is in milk.

Lactase persistence is needed to consume milk beyond early childhood years.

W. (Mr.)

So what you are saying is that if an African drinks a lot of milk his skin will become white.

[dna]

What has lactase persistence got to do with light skin?

Vitamin D is in milk.

Lactose is in milk.

Lactase persistence is needed to consume milk beyond early childhood years.

W. (Mr.)

[1798]

You didn't explain how you know what part of the selection coefficient it due to what mechanisms. The paper I referenced actually provided a way to get at one aspect of it. They looked at ancient DNA in southern Europe where lack of sunlight would not be an issue and still found strong selection for lactase persistence. They can't say what causes the selection but the vitamin D mechanism seems to be ruled out for these samples.

What has lactase persistence got to do with light skin?

[PNGarrison]

You didn't explain how you know what part of the selection coefficient it due to what mechanisms. The paper I referenced actually provided a way to get at one aspect of it. They looked at ancient DNA in southern Europe where lack of sunlight would not be an issue and still found strong selection for lactase persistence. They can't say what causes the selection but the vitamin D mechanism seems to be ruled out for these samples.

[lgmayka]

"Political correctness" is a common insult in political "arguments," but it doesn't have much relevance in science.

You are correct that political correctness has no place in real science, but we nevertheless see it often--very often in pop-sci articles written by sensationalistic journalists, but sometimes even in scholarly papers, due either to the authors' own bias or simply as a way to get through peer review.

In late 2012, some authors--one of whom is personally known to me--published a paper with important new data. The paper's conclusion, however, gave a politically correct and totally unjustified interpretation. The author known to me later confided that the conclusion had to be written thus, otherwise powerful people in academia would never have permitted its publication, at least not in a timely fashion.

The general rule in academia is: If the data is reliable, great! Use it! But form your own conclusions. In particular, a graduate student trying to get his PhD in a reasonable timeframe is not going to waste three years of his life debating his thesis' conclusion with powerful people--he will simply rewrite it the way they want it. He knows that the data is the valuable, enduring part of the thesis anyway.

[PNGarrison]

Direct Estimates of Natural Selection in Iberia Indicate Calcium Absorption Was Not the Only Driver of Lactase Persistence in Europe

http://mbe.oxfordjournals.org/conten...ev.msu049.full

Interesting in regard to this area. They rightly refer to the proposals on mechanisms as "speculation."

[PNGarrison]

"Why do I get the impression that this article is about shoring up the recent paper on a massive invasion from the Steppe in to western Europe 4,500ybp?"

The article on natural selection used the same data set as the recent paper about the steppe "invasion."

[PNGarrison]

"Even lactase persistence does not bestow a purely biological advantage per se so great as to explain its rapid predominance in Northern Europe and its considerable presence even in Southern Europe. After all, there are plenty of other foods to consume besides raw milk. Rather, social behavior must also have played a role, just as it does today: Once milk-drinking becomes common in a society (or at least among the privileged class), those who are lactose-intolerant are considered diseased or at least annoying, and therefore socially disadvantaged."

How do you know what part of the selection coefficient of lactase persistence or light skin is attributable to a direct biological effect or to social effect? I've never seen any way to measure that. You can measure an allele frequency at one time and at a later time and calculate a selection coefficient but it is extremely difficult to tell what mechanisms contribute to it.

You are making an assertion, but I can't see what objective support you have for it. "Political correctness" is a common insult in political "arguments," but it doesn't have much relevance in science.

[Armando]

You will have to change your opinion whenever they find ancient R1b lines in the Isles.

If they find R1b-M269 from 5,000-7,000 years ago then I will accept the science that proved it. For now, the observable data tells us that won't happen.

[1798]

You don't have to accept science if you don't want to. Just don't expect logical people to side with you.

You will have to change your opinion whenever they find ancient R1b lines in the Isles.

[Armando]

Why do I get the impression that this article is about shoring up the recent paper on a massive invasion from the Steppe in to western Europe 4,500ybp?

You don't have to accept science if you don't want to. Just don't expect logical people to side with you.

[1798]

The portion of the article that you had quoted didn't say anything about 4,500 ybp or that it didn't exist in the Mesolithic. If your beef wasn't with what was quoted in the article why did you quote it?

Now that you have expressed what your beef is with. Why do you ignore what I quoted where they state not all of Europe had the rs1426654 SNP in the Mesolithic? Why do you ignore that page 11 of the PDF show it to be in 100% of modern populations of Italians, Central Europeans, British, and Finnish but not 100% of Mesolithic or Early and Middle Neolithic Europeans?

Why do I get the impression that this article is about shoring up the recent paper on a massive invasion from the Steppe in to western Europe 4,500ybp?

[Armando]

I know that it is but it is also more than 4,500 ybp so the SNP rs1426654 is a north western European Mesolithic SNP.

The portion of the article that you had quoted didn't say anything about 4,500 ybp or that it didn't exist in the Mesolithic. If your beef wasn't with what was quoted in the article why did you quote it?

Now that you have expressed what your beef is with. Why do you ignore what I quoted where they state not all of Europe had the rs1426654 SNP in the Mesolithic? Why do you ignore that page 11 of the PDF show it to be in 100% of modern populations of Italians, Central Europeans, British, and Finnish but not 100% of Mesolithic or Early and Middle Neolithic Europeans?

[lgmayka]

I must once again emphasize that slight biological advantage does not explain rapid fixation.

Even lactase persistence does not bestow a purely biological advantage per se so great as to explain its rapid predominance in Northern Europe and its considerable presence even in Southern Europe. After all, there are plenty of other foods to consume besides raw milk. Rather, social behavior must also have played a role, just as it does today: Once milk-drinking becomes common in a society (or at least among the privileged class), those who are lactose-intolerant are considered diseased or at least annoying, and therefore socially disadvantaged.