Monday, April 26, 2010

Diet, disease, and pigment variation in humans

Some interesting hypotheses about the relationships between skin pigmentation, vitamin D, and immune response in Europe.

Diet, disease and pigment variation in humans.
Med Hypotheses. 2010 Apr 19. [Epub ahead of print]
Abstract: There are several hypotheses which explain the de-pigmentation of humans. The most prominent environmental explanation is that reduced endogenous vitamin D production due to diminished radiation at higher latitudes had a deleterious impact on fitness. This drove de-pigmentation as an adaptive response. A model of natural selection explains the high correlations found between low vitamin D levels and ill health, as vitamin D's role in immune response has clear evolutionary implications. But recent genomic techniques have highlighted the likelihood that extreme de-pigmentation in Eurasia is a feature of the last 10,000years, not the Upper Pleistocene, when modern humans first settled northern Eurasia. Additionally the data imply two independent selection events in eastern and western Eurasia. Therefore new parameters must be added to the model of natural selection so as to explain the relatively recent and parallel adaptive responses. I propose a model of gene-culture co-evolution whereby the spread of agriculture both reduced dietary vitamin D sources and led to more powerful selection on immune response because of the rise of infectious diseases with greater population densities. This model explains the persistence of relatively dark-skinned peoples at relatively high latitudes and the existence of relatively light-skinned populations at low latitudes. It also reinforces the importance of vitamin D as a micronutrient because of the evidence of extremely powerful fitness implications in the recent human past of pigmentation. Copyright © 2010. Published by Elsevier Ltd.

7 comments:

onur said...

But recent genomic techniques have highlighted the likelihood that extreme de-pigmentation in Eurasia is a feature of the last 10,000years, not the Upper Pleistocene, when modern humans first settled northern Eurasia. Additionally the data imply two independent selection events in eastern and western Eurasia.

If the results of these techniques are true, they can also be interpreted in a different way: Maybe Upper Pleistocene anatomically modern people of northern Eurasia were almost totally replaced by the Neolithic colonists (farming and/or herding) during the Holocene. So with this replacement, Upper Pleistocene anatomically modern people of northern Eurasia, who were already de-pigmented from their earliest times in northern Eurasia and whose de-pigmentation genes were totally (or almost totally) different from today's populations, would be replaced by the Neolithic colonists (who, of course, were also anatomically modern), who had more or less the same de-pigmentation genes with today's northern Eurasian populations. The difference between eastern and western Eurasia in de-pigmentation genes can easily be explained with different Neolithic source populations for them. This scenario also explains the sudden appearance and spread of the Mongoloid phenotype (never seen anywhere during the Upper Pleistocene) in eastern Eurasia during the Holocene. Also Upper Pleistocene anatomically modern Europeans don't look like Holocene Europeans (including today's Europeans).

Anonymous said...
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Richard said...

Vitamon D deficiency is commonly cited as the reason for blond hair amongst Filipinos, who normally have universal black hair.

Admittedly seaweed and coin collectors are very ooor, but is this due to their sun exposure or to Vit D deficiency?
http://www.marketmanila.com/archives/a-lato-gatherer

onur said...
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onur said...

What are your observations and knowledge about the existence of natural blond hair among Filipinos and the other totally or almost totally non-Caucasoid ethnicities? How frequent is it among them, and in what types? Also is it genetic, environmental (poor nutrition (esp. of vit D), exposure to sun, etc.) or a combination of the two? If it is genetic (at least partially), I wonder which genes are responsible and if they are the same or similar to those of the Caucasoid (at least partially) blonds? Everyone's response is welcome.

Btw, is the hair of that blond man in the photos natural or dyed?

THE_TRUTH said...

Hi Onur

In your post:

"This scenario also explains the sudden appearance and spread of the Mongoloid phenotype (never seen anywhere during the Upper Pleistocene) in eastern Eurasia during the Holocene."

It's me"

I have an interest in the mongoloid phenotype. Could you recommend any sources (research papers), related to the above snip.

My e-mail is: markwhouston@netvigator.com

martha said...

the data imply two independent selection events in eastern and western Eurasia, therefore new parameters must be added.

bioinformatics training india

 
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