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Yoshiura, Koh-ichiro, et al. “A SNP in the ABCC11 gene is the determinant of human earwax type.” Nature genetics 38.3 (2006): 324-330.
When I was in college a Korean American friend confided to me that his roommate had an issue. He had seen a q-tip in the waste-bin, and what was at the end of it was shocking to him. What my friend was describing was wet earwax (Google it yourself if you want to see it). As this was the first time he was living with a non-Korean he had assumed that everyone’s earwax was dry, like his own. The maps above and to the left show you the frequencies of the allele which has an extremely strong correlation with this trait. In Korea the frequency of dry earwax is close to 100%. Since the expression pattern for dry earwax is recessive, you need two copies of the derived allele, so in any population where the ancestral variant exists in appreciate frequencies you’ll have the wet variant of the trait.
This is why in 2006 a Japanese group published research in this area, A SNP in the ABCC11 gene is the determinant of human earwax type. A substantial minority of Japanese happen to have wet earwax. And it turns out that wet earwax has some other associations of interest.
Nakano, Motoi, et al. “A strong association of axillary osmidrosis with the wet earwax type determined by genotyping of the ABCC11 gene.” BMC genetics 10.1 (2009): 42.
Axillary osmidrosis is scientific for body odor. These results show a very strong association between someone with the ancestral allele which results in wet earwax, and strong body odor. Obviously this is a “news you can use” sort of result, so no surprise at seeing this paper: Dependence of Deodorant Usage on ABCC11 Genotype: Scope for Personalized Genetics in Personal Hygiene:
Earwax type and axillary odor are genetically determined by rs17822931, a single-nucleotide polymorphism (SNP) located in the ABCC11 gene. The literature has been concerned with the Mendelian trait of earwax, although axillary odor is also Mendelian. Ethnic diversity in rs17822931 exists, with higher frequency of allele A in east Asians. Influence on deodorant usage has not been investigated. In this work, we present a detailed analysis of the rs17822931 effect on deodorant usage in a large (N~17,000 individuals) population cohort (the Avon Longitudinal Study of Parents and Children (ALSPAC)). We found strong evidence (P=3.7 × 10−20) indicating differential deodorant usage according to the rs17822931 genotype. AA homozygotes were almost 5-fold overrepresented in categories of never using deodorant or using it infrequently. However, 77.8% of white European genotypically nonodorous individuals still used deodorant, and 4.7% genotypically odorous individuals did not. We provide evidence of a behavioral effect associated with rs17822931. This effect has a biological basis that can result in a change in the family’s environment if an aerosol deodorant is used. It also indicates potential cost saving to the nonodorous and scope for personalized genetics usage in personal hygiene choices, with consequent reduction of inappropriate chemical exposures for some.
I don’t want to get into the biology of this is too much detail. Suffice it to say that the SNP in ABCC11 has a lot of effects. It looks like there might have been a selection event to drive up its frequency at some point. I’m intrigued at the fact that among European populations it is among Sardinians that the derive allele is least common. If it was selection I’m pretty sure don’t know the target phenotype. Less body odor is probably simply a nice side effect. Ultimately though this is personal. If you read NPR’s stupid Code Switch blog you will have seen that Study Says Your Race Determines Your Earwax Scent. Actually, obviously no. This gene has a high between population difference as far as genes go, but the wet and dry phenotypes segregate in many families, and are found in appreciable frequencies in many populations. Both alleles are found in my own immediate family. My wife and myself carry both alleles. We’re heterozygotes. My daughter is a homozygote for the ancestral variant. My soon-to-be-born son is homozygote for the derived variant. Perhaps we’ll be saving on deodorant purchases?
Wow, Razib, you just changed my whole view of myself!
I always assumed I had typical European earwax, because it’s yellowish, and I heard Asian earwax was grayish. It’s always caused me issues however, because it never falls out of my ear canals, instead forming hard plugs that I got painfully “flushed” periodically as a child.
I have also basically never used deodorant in my life, aside from a few times in high school. I sweat profusely over most of my body when I’m warm or exerting myself, but not particularly from my armpits, and I’ve never been able to detect any significant armpit odor. The women I have dated have all remarked on how little body odor I had, and were amazed I didn’t use deodorant, so I knew it wasn’t all in my head.
So I read your post and was like…wait, Asians have dry earwax…I thought they had wet, because I have dry! And then I went to 23andme, and realized yes, I do have the “Asian” variant. I am TT, and my mom is CT (my dad must have been as well). I’m feeling dumb right now, but my essentially life-long abstaining from deodorant now makes sense.
As a non-specialist all I can say is that a lessening of body odor should be a valuable trait among hunter gatherers. Combat veterans can attest that under field conditions soldiers can literally smell the enemy. Hunters know that staying downwind of prey is crucial.
Agriculturalists on the other hand can smell for all the plants care.
I have a theory that dry ear wax developed as an adaptation to cold. If many East Asians’ ancestors originated in the cold and dry Siberian Arctic, it probably would have helped to have dry ear wax, which wouldn’t freeze in the ear canal. Less body odor was just an auxiliary effect of this allele.
it probably would have helped to have dry ear wax, which wouldn’t freeze in the ear canal.
doesn’t really explain the pattern though. why isn’t near fixed in russians? there’s a lot of it floating around.
a lessening of body odor should be a valuable trait among hunter gatherers.
the highest frequencies are found in korea and north china. ppl have been farming a long time there.
funny story karl.
there are some pretty gross earwax removal vids on youtube if anyone wants examples of the different types.
Any non-Asians who picked up this trait from two heterozygous parents, I recommend East Asian ear grooming products, if you aren’t familiar with them. You can get these little bamboo sticks that are shaped like a tiny spoon on one end that you can use to clean out your ears. It sounds weird and gross, but I think it’s more effective for cleaning than Q-Tips, which seem to just jam the wax further in if you have dry ear wax.
My soon-to-be-born son is homozygote for the derived variant. Perhaps we’ll be saving on deodorant purchases?
Especially if he’s a HS athlete. You ain’t smelled anything until you’ve been downwind of a HS athlete’s gym bag. Phew!
This research stinks of racism.
PSA: You should NOT stick q-tips in your ear canals! Bad bad bad.
http://en.wikipedia.org/wiki/Cotton_swab
http://ent.med.nyu.edu/news/why-not-stick-cotton-swabs-your-ear
The assertion by Japanese researchers that the Japanese population, in general, lacks axillary odor is completely fallacious. I am a white guy who rides the Tokyo subways, sardine-style, to and from work each morning. In summer when we are all doing “cool biz” (and hence the air-conditioning is turned off), the salary men indeed carry a pungent malevolent odor. It is simply a different odor from the one described for Westerners.
I’m CC and I don’t use deodorant normally. Oh dear!
I have the dry ear wax variant, confirmed by genotyping (which is a bit surprising) and have never needed to use deodorant. As a teenager I started using it, just on assumption, but stopped again when I realised there was no point.
In fact, I’m pretty much the way Karl Zimmerman describes himself.
My daughter is also the same, and has never needed to use deodorant.
My northern Chinese wife just assumes she needs it because the advertisements say so, but in fact she never does need it. She has a very mild body odour that is noticeable to me because it is different from what I was familiar with growing up, but it is not unpleasant, just different. She says I smell very mildly like a sheep, which she does not find unpleasant, just different.
I once got stuck walking in amongst the Chinese national women’s volleyball squad, all very tall women, after they had been on a training run, and the smell was Heaven on earth. Definitely not offensive, quite the opposite, but by then I was accustomed to what I think of as Chinese natural smell.
I laughed a little reading Nicholas Wade’s new book because two of the main examples of evolution since the exodus from Africa he describes in the early part of the book were lactose tolerance and dry earwax. I make a pretty terrible Caucasian using just these examples since I’m lactose intolerant and have dry earwax.
I can attest to the associated lack of body odor, too. I used deodorant when I reached puberty because I was “supposed” to but gradually quit since I didn’t see any point. This was all before I had any clue about different types of earwax. Nowadays I am still deodorant free and no one ever complains. Karl’s experience sounds very familiar.
Fun. I had always assumed that differences in body odors were a purely environmental matter linked to our eating habits (like people from the Sahel region in the metro smelling distinctly like allspice, which beats white people smelling like mildly rotting flesh according to some Africans).
@ Sandgroper: lucky bastard
I once forgot to bring deodorant with me to S. Korea, and did not realize this until I was already few hours S of Seoul. I searched many local stores to buy deodorant, but it not for sale anywhere, and the Korean contacts I saw traveling with nor the hotel had any idea where to find it.
It was an uncomfortable trip, until I got back to Seoul where I could find an international hotel that had deodorant for sale.
I am of Greek descent, have sticky earwax, sweat profusely, and generate quite strong body odor.
“white people smelling like mildly rotting flesh” LOL
“My soon-to-be-born son is homozygote for the derived variant.”
I read right past that sentence without much impact until I paused and reflected that the ability to make such a statement without extraordinary efforts or expenditures would have been blow-your-mind worthy not that long ago, and completely unbelievable not too long before that. How quickly we become assimilated to the radical.
Long time resident of Japan, with trips to other Asian countries. Japanese certainly have a distinct, and sometimes unpleasant body odor. Nothing like some Chinese though, who sometimes smell strongly of rancid butter. I suspect it is mainly a question of what odor you are used to. Thai people, and also Central American Native Americans seem to have almost no body odor. Something else is going on besides this one gene variant.
My Japanese wife says I really smell after sweating.
I don’t know about human detectable odor, but human sweat apparently does uniquely attract mosquitos because of the contents of eccrine sweat-
http://pawsoflife-org.k9handleracademy.com/Library/Scent/Smallegange_2011.pdf
“Humans have a large variety of carboxylic acids and a high amount of lactic acid on their skin. These unique characteristics might enable anthropophilic mosquitos to distinguish humans. Ammonia and lactic acid, mainly present in eccrine sweat, in combination with the carboxylic acids resulting from microbial conversion of apocrine and sebaceous secretions, seem to be at least partially responsible for attraction of Ae aegypti and An. gambiae s.s. to humans”
The sensitivity of mosquitos to human sweat might suggest a selective story…? Anti-malaria adaptions are some of the most recently selected.
Particularly if other genetics (EDAR) have generally enhanced gland development, as the East Asian dominant variant of EDAR appears to have done to the eccrine glands (http://www.sciencedirect.com/science/article/pii/S0092867413000676 – “We find that EDAR370A is associated with an increased number of active eccrine glands in the Han Chinese”). An extra-strong scent attraction to mosquitos (possibly still present in East Asians with the derived EDAR370A and ancestral ABC11) driven by increased eccrine secretions might make a variant like ABC11, apparently disfavorable elsewhere, suddenly have a favorable selective payoff.
Does this dry variant correlate to sweating (a.o.) less salts and such per se, and subsequently less osmotic effects drawing water to the outside of the skin?
Adaptive trait in a relatively cold and dry (sort of like a dessert) area -maybe somewhere around the north of China, where the trait seems most dominant? Just guessing
23andMe states that the protein encoded by rs17822931 is also turned on in breast tissue, where it appears to be associated with colostrum production. Since colostrum is known to have protective effects on newborns, and dry earwax is associated with reduced production, the derived variant presumably must have a strong off-setting advantage elsewhere.
“the protein encoded by rs17822931 is also turned on in breast tissue, where it appears to be associated with colostrum production”
A Japanese girlfriend I once had told me I smelled like milk. That may be why!