Son of Edar

The EDAR V370A variant, almost fixed in northeast Asia, is known to cause coarser hair,  smaller breasts with increased branch density,  shovel-shaped incisors,  more eccrine sweat glands, and changes in the shape of the earlobe. The changes in eccrine sweat glands and the hangey-down part of the ear have only been noticed recently.

It’s a gain-of-function mutation: you’re getting more of the effect that EDAR normally has.

Some people have loss-of-function mutations in EDAR: hypohydrotic extodermal dysplasia, HED.  This was first identified by Charles Darwin. In The Variation of Animals and Plants under Domestication, he noted a family in India that produced ten men in four generations, all suffering from missing teeth, very little hair, inability to sweat, etc.

HED patients also have messed-up fingernails and have problems with the lacrimal glands (tear glands), the sebaceous glands, the Meibomian glands, and salivary glands. Presumably you would see the opposite effects in people with a gain-of-function mutation like EDAR V370A.

So – somebody should look for characteristic racial differences in tears, sebaceous glands, Meobomian glands, and salivary glands. And possibly fingernails. They may well exist,  be driven by this EDAR mutation, and some might play a role in its selective advantage.

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27 Responses to Son of Edar

  1. JayMan says:

    “he noted a family in India that produced ten men in four generations, all suffering from missing teeth, very little hair, inability to sweat, etc.”

    So I have to ask: did that mean that the women in that family had larger than average breasts?

  2. Matt says:

    HED patients lack apocrine glands too.

    Presumably you would see the opposite effects in people with the gain-of-function mutation like EDAR V370A, as well.

    But mutations in ABC11 (dry earwax) might offset this, so you’d want to control for that.

    That’s hard to do in some populations, like Koreans were derived variants at ABC11 and EDAR V370A are both at fixture.

    Easier in a population where neither ABC11 or EDAR V370A are near fixed for either derived or ancestral. Uyghurs would be good.

  3. The fourth doorman of the apocalypse says:

    Is there a consensus about this?

    Moreover, traditional theoretical knowledge of the human doesn’t really exhibit the virtues belonging to scientific theoretical knowledge. It doesn’t command consensus.

    To what extent is it the case that consensus is a part of the scientific method or scientific theoretical knowledge?

  4. Anahita says:

    For some reason, genes that affect dermal traits in mammals seem also to affect teeth since weirdness in both correlates.

    Rabbits and hares possess such odd skin & teeth that past authors actually failed to identify them as placentals. Their teeth possess cusps and folds that have proved almost impossible to homologise with those of other placental mammals, but perhaps resemble a primitive triconodontids; the soles of their paws are hairy; and they do not suckle their young like other placentals, Instead, the milk is ejected in one big squirt just like a marsupial.

    Whales must have the weirdest skin in mammals, and also the oddest teeth – the uniformity of a toothed whale’s teeth is because they are not properly homologous to the dental formulae of other mammals, but are supernumerary denticles.

    If true then tooth characters might be useful in inferring soft-tissue states that rarely preserve, for example, hair in a proto-whale such as Dorudon or Basilosaurus.

  5. Erik Sieven says:

    From personal experience I would guess East Asians have less tears. That makes sense, as the low nasal bridge and thus the smaller tear tube between eye and nose of east asians makes it harder for tears to get out of the eye. So less tears is good when you have a low nasal bridge

  6. Acres of Statuary says:

    “The meibomian glands are … responsible for the supply of meibum, an oily substance that prevents evaporation of the eye’s tear film.”

    Hmm. When the temperature is below -30 C my eyes produce plenty of tears but then my eyelids tend to freeze together. A cold weather adaptation?

    • A cold weather adaption?

      It could very well be. I am looking forward to more ancient human bones with well preserved DNA giving us answers to these questions in the upcoming decades. Time has been incredibly and sadly effective in erasing our past. If the past five years is any indication of the future than more bones from Asia’s far north with their DNA protected from decay by permafrost will tell us far more than we already know. I am going to guess that small pockets of humans living in refugiums during the ice age expanded rapidly once the hard times of the ice age ended carrying with them such traits as this variant of EDAR.

      So what else happens to a population of humans living in a very hard environment to live in such as an ice age refugium as compared to a population living far to the south? They evolve to be more intelligent. The evidence isn’t there to substantiate this yet but it seems rather obvious and I hope to live long enough to see all the hubbub that springs forth when it does.

  7. Sean says: More common in Whites
    The bald guy out of the original the Hills Have Eyes.

  8. Sean says:

    It’s most likely an anti-parasite thing for Han farmers who used human excrement as fertiliser.

    • gcochran9 says:

      Can’t be, too old: common in Amerinds, including hunter-gatherers.

      • Sean says:

        It’s most common in Han. Whatever it’s for, Han needed it more than the rest of humanity. Caleb Finch doesn’t seem to think hunter-gathers didn’t need protection from parasites.

        OVER time, eating red meat, particularly raw flesh infected with parasites in the era before cooking, stimulates chronic inflammation, Finch explained. In response, humans apparently evolved unique variants in a cholesterol-transporting gene, apolipoprotein E, which regulates chronic inflammation as well as many aspects of aging in the brain and arteries. One variant found in all modern human populations, known as ApoE3, emerged roughly 250,000 years ago, ‘just before the final stage of evolution of Homo sapiens in Africa,’ Finch explained.”

  9. The fourth doorman of the apocalypse says:

    OT, from here:

    Click to access Graves_and_Peichel_2010.pdf

    Sex determination in birds and snakes is also accomplished by means of sex chromosomes, but they are completely the converse of the mammalian system. Males have two copies of a gene-rich Z chromosome, and females a single copy of the Z and a small heterochromatic W chromosome. The Z has been shown by chromosome
    painting and gene mapping to be identical in all bird species
    , but is not homologous with the mammalian X

    The highlighted portion is striking. Is the Z in birds really that conserved? Is that what they mean?

  10. TWS says:

    Does the fossil record show archaics in Asia with that same tooth type?

    • Joyce Song says:

      Yep, there were “Peking Man” living near Peking around 700kya (re dated by new tech.), already adapted to quite cold climate. His brain volume was over 1200cc, within modern human range and larger than regular H. Erectus, but still with very prominent brow ridge (more than late Neanderthals). There was another quite complete fossil dated around 250kya and further north (40 degree N latitude), thought to be a male initially because of her size, about 5’7″ and170 lb and her brain volume about 1,350cc. Humans originated from more than one lineage, diverged 2 mya, then gene flow around 1 mya and again around 130kya (or 200yka?). A variant of MCPH1 diverged about 1 mya from the version more common in Africa. HLA-B*73:01 is 16 my old and has pattern more similar to that of apes, 5% in a population in Pakistan and low around southern Europe and North Africa and 2% in two groups of Amerindians. The frequency of shovel shaped teeth is less than 5% in Europe, 10-12% in Arabs, 20-25% in Egypt and present in San people too and I am sure in Central Asia population with some East ancestry too. There must be more than one gene control tooth characteristics, Shovel shaped teeth (Sinodonty) are actually smaller than other teeth(Sundonty), but the shovel shape makes them stronger for the size. Amerindians have similar teeth as East Asians, both definitely have same cold adapted northern lineage and they have more of haplo B006 in X chromosome (1 my old) and some Europeans have it too.

  11. AA person says:

    370A G allele in Finns correlates nicely with East-Asian admixture, with an average frequency of 5% in the samples used by Yales ALFRED. Seems it hasn’t provided much if any advantage over the period of 4000 years since it’s presumed introgression into Finland.

  12. Greying Wanderer says:

    “Women who are carriers for XLHED may have some symptoms, such as thin hair, reduced sweating, one or more missing teeth, and sometimes have difficulty breastfeeding.

    Seems to me if iodine is needed for brain development and iodine mostly comes from the sea then hominids in the Eurasian interior (or up mountains) might have been retarded (relatively speaking).

    If so archaics in the Eurasian interior, especially up mountains like the Himalayas might have developed something that compensated or partially compensated for this lack of iodine – not necessarily making them smarter than the fish eaters nearer the coast but not as dumb as they would otherwise have been.

    The big advantage would come if/when the people who’d got that interior/mountain adaptation off the archaics mixed with people from or moved to regions where they got the iodine as well.

    Seems to me the obvious place to have adaptations to improve child brain development when it’s growing most i.e. between the ages of 0-3, is breast milk.

  13. CT says:

    Hey cool, I have Hypohydrotic Ectodermal Displaysia.

    Ive sometimes considered whether there might be some selective advantage to HED, but it always seemed far-fetched to me. My best supposition has been that sedentary life in confined climate-controlled spaces, selects for hairless sweatless mole people.

    My cousin, my great-grandfather, and two of my mom’s cousins have HED, and among the five of us, four of us are (or were) engineers. Its n=5 so maybe thats just a coincidence (my mom, her sister, and my grandmother, and my grandmother’s sister have HED too but, its not a dominant trait for women).

    • reezy says:

      So since this condition in your family is sex-linked (presumably on the X-chr), then this must mean it’s a mutation of some different gene compared to the V370A variant of the EDAR gene then, which is located on chr2 apparently.

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