Because most philosophies that frown on reproduction don't survive.

Friday, September 07, 2007

How Now Brown Frau?

I've always wanted to use that title, and it's been a while since I've pulled in some hard core science/genetics content.

Razib of GeneExpression has a lengthy post up on a recent paper looking at the genetic basis for skin color variation in South Asian populations. A couple of interesting take-aways (as I understand them) for the person not up for reading about specific genes:
  • Despite the massive cultural movements in and out of India and Europe in the last 10,000 years since the end of the last ice age, in both regions the majority of the ancestors of the population go back to the end of the last ice age.
  • The highest caste (and often lightest skinned) groups within India have the highest proportion of non-Indian ancestry (going back 10k years).
  • The overall skin color difference between the African and European populations is primarily the result of a single gene which is set differently in each population. Variations in skin color within each population are then the result of variation in other genes that affect skin color.
  • Skin color in the East Asian population is the result of different genes, thus suggesting a longer term population separation.
  • In the case of South Asians, variation in skin color is to a great extent the result of variation in the same gene that controls the primary difference between European and African skin coloration -- and yet the appearance of that gene doesn't seem highly correlated to other neutral markers that would suggest European genetic input. That suggests that both populations have independently begun selecting for the same mutation in that gene (producing light skin color) within the last 10,000 years.

Anyway, if that's not already genetics for you, go check out Razib's post, since he actually knows what he's talking about, and I'm just a clever and interested parrot. Or, if you've no interest in genetics, some may still want to check out the Bollywood babes whom Razib uses to illustrate his skin tone point. You know who you are.

UPDATE: See Razib's comment for a few clarifications, explanations on my bullets above.

4 comments:

Razib said...

minor clarifications:
The highest caste (and often lightest skinned) groups within India have the highest proportion of non-Indian ancestry (going back 10k years).

the highest caste within a region is usually the lightest. but the highest castes as a whole exhibit lot of variance so that the highest caste in tamil nadu might have darker skin than a low caste punjabi. i suspect that in situ selection is also part of the factor here.

The overall skin color difference between the African and European populations is primarily the result of a single gene which is set differently in each population.

well, it is 25-40% of the between group variance, so i don't know about 'primarily.' rather, it is a gene of large effect, and probably larger.

That suggests that both populations have independently begun selecting for the same mutation in that gene (producing light skin color) within the last 10,000 years.

yes. it is the same SNP. so like lactase persistence it seems that the region from europe to india can be thought of as a unified gene pool to a far greater extent than europe-africa-asia. to be 'old school' about it the 'caucasoid' race is probably the creation of the last 10,000 years due to these pan-regional dynamics, not deep ancestry.

Darwin said...

Thanks for the corrections, Razib. I put an update pointing towards them. I guess I should know better than to try to summarize so extensively on the fly.

Rick Lugari said...

Glad you provided a link, but unfortunately I now have that stupid song in my head. You know -

Hooray for Bollywood
That screwy, ballyhooey Bollywood
Where a Kwikie Mart clerk named Apu
Can be a panic, with just a slushy in a can

Herdingcats said...

This taste for light skin, it must be new. Darker skin has fewer visible blemishes, it wrinkles less, it is less apt to get cancer, and it has a great sheen to it. Dark skin is more attractive except for the fact that it's dark.

Logically, this does not make sense. I think that the taste for light skin is from the Middle Ages onward. The ancient Romans referred to the British as thugs and bad slaves. The Romans praised Ethiopians as being much smarter than any other group of slaves. In Medieval Venice, Moors were a noble class (ala Othello). Race-based slavery is only as old as the Conquistadors of Spain and Portugal.

I believe that this racism based on lightness is an Anglo/Saxon (English/German) taste and therefore quite recent.

The question is, how can we change this madness.

Please click on my blog to read about a Catalan boy who is being harassed by the Spanish government because of his language and ethnic identity. herdingcatsgeorge.blogspot.com