Lunar / “Asian” New Years is always an occasion for me to reflect on how different South (brown) Asians are from East and Southeast (yellow) Asians. However, there is an area in which we, apparently, are a mix of both African/European and East Asian genotypes. The area in question is earwax:
Earwax comes in two types, wet and dry. The wet form predominates in Africa and Europe, where 97 percent or more of people have it, and the dry form among East Asians. The populations of South and Central Asia are roughly half and half. [Link]
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p>This is evidence, apparently, of some yellow in the woodpile:
The dry form, the researchers say, presumably arose later in northern Asia, because they detected it almost universally in their tests of northern Han Chinese and Koreans. The dry form becomes less common in southern Asia, probably because the northerners with the dry earwax gene intermarried with southern Asians carrying the default wet earwax gene. [Link]
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p>There must have been a lot of intermarriage if half the populations of South Asia have the East Asian gene. It turns out that the earwax gene is also related to that other, oh so polite topic of conversation, body odor:
Since it seems unlikely that having wet or dry earwax could have made much difference to an individual’s fitness, the earwax gene may have some other, more important function. Dr. Yoshiura and his colleagues suggest that the gene would have been favored because of its role in sweating. They write that earwax type and armpit odor are correlated, since populations with dry earwax, such as those of East Asia, tend to sweat less and have little or no body odor, while the wet earwax populations of Africa and Europe sweat more and so may have more body odor. [Link]
This would imply that half of all South Asians sweat little and have little B.O. Having recently ridden the Delhi metro, my question is … where are they 
?
i don’t have much BO. but i’m bengali, we have more east asian 🙂
thoug seriously, be careful about this “admixture” stuff. there weren’t original yellow, white and black people from whom south asians are derived by mixing. that is what the indians are indigenous research is trying to debunk! rather, what might have happened is that the “A” allele (2 AA’s = dry ear wax) was beneficial in south asia for whatever reason. you only need a small number of intermarriages for the gene to spread if it is a good thing…. (for example, 70% of north indians are not lactose tolerant because they are 70% european, it is because those genes, passed from population to population across eurasia, were fit in a north indian environment).
some readers might find my post on this topic of interest (it is over at my new Seed Magazine sponsored blog, so that is why the URL isn’t normal).
ok, and one last thing. consider that in a large population (drift is ignored) that the probability of fixation (going to 100% in the population) of a new mutation is 2s, where s is the selection coefficient associated with the allele. so, if allele A makes you 1% more fit than the population mean you have an s of 0.01. that means that the gene has a 2% shot at being dominant. now, consider that it isn’t a mutation, but introduced from a new population, to have an expectation of fixation (not a guarantee, but if you ran a simulation a shit load of times this would be the most frequency occurrence) you’d need 50 introductions (that is, .02*50 = 1). that’s fifty matings.
just to give you a sense that widespread admixture is not necessary in the case where selection is operative.
manish i dunno how much you have travelled India. We are not actually all brown. My opinion based on our genepool. Indian subcontinent has traces of almost all the genepools of the world. Other way of saying we have been a genetic melting pot for centuries if not less. I come from the northeastern part of india and we are not brown as you would sa but more oriental. yellow skin is a part of our identity and incidently we are very proud Indians too.
Mithya, I dunno whether you’ve checked the author of the post 🙂
Mithya,
You’re right, I was over-generalizing. I was just in India and was struck by how many “East Asian” type features I saw, even on brown skinned faces. I don’t mean to be exclusionary, this has been a part of the heritage of the region for a long time (as the ear wax shows).
Razib,
Point conceded as well. However, while this is possible, I have questions about the fitness of this gene – according to the article, people in the North needed to sweat less, so the gene persisted. In South Asia, I have trouble understanding how less sweating (and therefore less cooling) is an advantageous trait.
A completely understandable mistake. We all look alike 😉
Hmm .. nothing good coming in on the tipline?
Certainly not the Mumbai local trains.
HAW!!!
… she really stuck it to you dude … tsk tsk..
I was just waxing poetic, don’t sweat it.
I have questions about the fitness of this gene – according to the article, people in the North needed to sweat less, so the gene persisted. In South Asia, I have trouble understanding how less sweating (and therefore less cooling) is an advantageous trait.
i don’t buy their explanation. i think selection is at work to get “A” to a high level, but they don’t know what it is. this a common problem, it is often easier to detect selection on the genome than understand what is being selected on the level of the phenotype.
re: east asian features in south asia, well, bengalis can tell you that for true. i have relatives who could pass as burmese (though don’t tell ’em that), my family is from the region of bangladesh next to tripura.
it seems razib you are what you call Sylheti. well, we were part of manipur and if you go even further you will realise we were aboriginals who wide spread in that valley. in fact few believe the difference of language between sylheti and rest is because they are connected to to tipura and manipur and even to the 13th Jewish Tribe.
My bad Manish, guess too excited to calm down and write
it seems razib you are what you call Sylheti.
sylhetis aren’t that different from other bengalis (there are genetic studies which show a strong discontinuity between particular NE indian ppls and browns, eg nagas or mizos vs. bengalis, sylhetis cluster with bengalis, not mizos, nagas or manipuris). my understanding is that they regularly claim they are very different from other bengalis for nationalistic reasons (my father taught in sylhet for several years and everyone told them they were part of assam, not bengali. the same thing happens to my uncle who also teaches in sylhet).
less sweating (and therefore less cooling) is an advantageous trait.
well, there are parts of india that are actually cold. also salt-loss is a problem–maybe the british monopoly did a bit of selection?
(CAUTION: the following is an overtly bitter tirade against the public hygiene of many – and by many i mean MANY – men in india)
so would this explain why half of all indian men seem to have cultivated a stick-finger-in-ear-canal-and-vigorously-gyrate habit?
while i’m at it, if bass, jackson et al are done with their ear wax investigations, i wish they’d dedicate some time to the mucosal membranes of the indian male. apparently there’s gold to be found in dem nasal pasageways, at least one would suspect so from that other enduring routine, namely the stick-finger-in-nose-then-examine-contents-and-wipe-on-pant/lungi.
but wait, there’s more: the endless chorus of expectoration, the public pissing parade, the adjusting of family jewels by the bright light o’day…
(like i said at the beginning, GRRR ARGH BITTER BITTER BITTER…)
on a minutely more serious note, you know that uncle whose ear rims resemble those of a koala? i once remember hearing that the hairy ear rim phenomenon had been studied on the subcontinent because of the regional preponderance of this trait. might any of you know if there is any truth to this legend?
if so, all ye knights of the brown table better start investing in some braun ear hair trimmers. cuz what’s cute on a koala ain’t so cute on you.
this ends today’s chapter of mama eye for the brown guy. tune in next time when i take on…those narrow shouldered wife beater undershirts. aiyoh, endeh dhevamaaaay!!!
actually i think its a generalization of north east region ppl advancement is not much in there if see the area nagaland and mizoram then in tribial area not so much revolution is there .70% ppl are not educated even and 65% of ppl dont know abt the polling .they dont know name of president of india so generalization should be there