Ancestral proto-Eurasians may have had wavy hair

Australian Aboriginal child photographed in the late 1850s

The above chart is from The Simons Genome Diversity Project: 300 genomes from 142 diverse populations. The basic outlines of this tree were evident as far back as L. L. Cavalli-Sforza. But there were always small details that caused issues. In particular, were East Asians a more natural clade with Australasians or with Europeans? Today with both ancient DNA and whole-genome analyses two things are clear which might have been confounding earlier analyses:

  1. There has been gene flow between many East Asian and European populations. If you look closely at the ancient DNA work it is clear that East Asian gene flow is present in Mesolithic hunter-gatherers. Conversely, many northern Chinese have show low levels of West Eurasian ancestry (I suspect mediated through Mongols and Turks).
  2. The peoples of Australasia have Denisovan ancestry, which is distinct from anything found in East Asians and Europeans (small trace proportions of Denisovan in the former notwithstanding).

With these considerations accounted for, it seems clearer that the peoples of Oceania and East Asia descend from a common group that pushed from the west. And, the most ancient substratum in South Asia is also part of this broad family of peoples, who diversified in the period between 45 to 55 thousand years before the present. This is in contrast to the peoples to the west, who gave rise to Ice Age Europeans, Middle Easterners, and more distantly the “Ancient North Eurasians” who seem to be the first settlers of Siberia.

To understand the context for the emergence of characteristics and traits one has to understand the demographic histories and relationships between people. We are coming close to establishing the latter with good certainty for most groups. Though the sea levels separated New Guinea from Australia only within the last ~10,000 years, genetic work suggests that the differentiation between highland Papuans and Australian Aboriginals long predates this. If I had to hazard a guess I’d suggest that the huge ecological differences were probably critical in reducing gene flow between the wet and warm highlands of Sahul, and the broad deserts that occupied what became Australia.

Andamanese child

With that, I want to talk about hair form. Early physical anthropologists grasped onto this characteristic because it is so easy to define and measure. Hair can be straight, wavy, curly, and tightly curly (“woolly”). Even within tightly curled hair, there is variation. The San Bushmen have “peppercorn hair,” which means its curl is tighter than that of their Bantu neighbors.

One assumption that many people make is that originally anatomically modern humans had tightly curly hair, rather like modern Africans. Additionally, the depictions of Neanderthals I’ve seen do not give them this form of hair. Though there are mutations that change hair form (no surprise they are shared with dogs and cats), looking at the minimal literature on this trait it seems that curliness is somewhat polygenic. It doesn’t segregate like a Mendelian trait.

Likely one reason that curly hair is presumed to be ancestral is that many of the Australo-Melanesian peoples exhibit similar hair form to Africans, and these people have long been thought to be more “ancient.” But this is a fallacy. The ancestors of the Andamanese and Negritos of Southeast Asia are no more ancient than those of the Han Chinese. All descend from the same group of people who pushed eastward around 50,000 years ago.

Until recently I had assumed that the best model for the indigenous people of South Asia, the “Ancient Ancestral South Indians” (AASI), were the Andamanese. And yet one group in south India, the Paniya, are ~75% AASI in their ancestry. Looking through photographs of this tribe with a keen eye toward hair form, though their hair is curly, on the whole, no individuals show extremely tight curls.

And of course, Australian Aboriginals famously, on the whole, do not have tightly curled hair. Most of them are wavy haired (though curlier hair form is more common on the northern coast).

Where does this leave us? Of non-African descendent populations, there are a diverse set of lineages. None of the people of West Eurasia have tightly curled hair. Of those to the east, only the Negritos of South and Southeast Asia, and the people of Melanesia do so. But the Australian Aboriginals, who are closer to Melanesians than any other population, do not have tightly curled hair (though the Tasmanians, who separated from the Aboriginals ~10,000, may have had so based on the photographs). The peoples of Northeast Asia and the Americas, do not have tightly curled hair, obviously.

The primary confound here is selection. Hair form is a polygenic trait. It is not unreasonable to think that the humans moving out of Africa would carry standing variation, and that selection for curlier hair in some tropical climates would result in convergent evolution. The ancestors of Papuans and Negritos then may have had wavy hair, and Australian Aboriginals simply maintained this.

Ultimately doing the same thing with hair that was done with pigmentation will probably answer the questions of ancestral-derived states.

10 thoughts on “Ancestral proto-Eurasians may have had wavy hair

  1. “This is in contrast to the peoples to the west, who gave rise to Ice Age Europeans, Middle Easterners, and more distantly the “Ancient North Eurasians” who seem to be the first settlers of Siberia.”

    Isn’t the highest portion of ANE found in modern east eurasian groups though?

    This is from the ANE article on wikipedia.

    “Flegontov et al. (2015) found that the global maximum of ANE ancestry occurs in modern-day Kets, Mansi, Native Americans, Nganasans and Yukaghirs.”

  2. that paper found some weird things. the position of ANE is confused cuz it looks like ANE contributed to BOTH west and east eurasians and no longer exists in ‘pure form.’

    if you disagree with flegontov, the highest ANE is arguably in amerindians and north caucasus.

  3. “Ultimately doing the same thing with hair that was done with pigmentation will probably answer the questions of ancestral-derived states.”

    I’ve only seen a handful of results. But, so far all Mesolithic Europeans carry a variant associated with very straight hair in modern Europeans. They might have had excessively straight hair.

    WHG in western Europe, was the only group in Late Paleolithic/Mesolithic west Eurasia homogeneous for dark skin allele in rs1426654. Russian, Ukrainian hunter gatherers were homogeneous for light skin allele. Most Scandinavian, Baltic hunter gatherers had the light skin allele.
    A large majority of hunter gatherer ancestry in modern Europeans is
    from eastern Europe not western Europe.

    Anatolian & Iran & Caucasus Paleolithic pops were also almost homogeneous for light skin allele in rs1426654.

    The Ala111Thr allele (rs1426654) allele has greatest effect on skin color in detected variants. But, both mostly brown skinned southwest Asians & white skinned Europeans have it. So, it can’t differentiate between those two skin tones.

    Still, safe to say skin color of west Eurasians was already “lightened” in Epipaleolithic/Mesolithic.

    The main event of pigmentation selection seen in ancient DNA from Europe is for blue eyes, blonde, red hair not skin color. It only affected northern Europe and originated in northern Neolithic farmers maybe especially Globular Amphora. In Globular/Corded Ware mixed populations, the traits from Globular were favored by selection & remained very popular.

  4. not much work in this area though
    But quite a bit of social studies and even a recent movie. In the folk wisdom of Latin America, informed by centuries of admixture combined with racism, it is the curliness (“pelo malo”), rather than color, which is used as a proxy for fractional African ancestry. Implying that the trait is EXTREMELY polygenic. Of course the folk wisdom may or may not be a good match to the actual genetics, but these populations accumulated so much historical experience that I’d be surprised if they were far off the mark.

  5. Didn’t the recent study of Iberomerusian DNA indicate that they had dark skin, yet straight(ish) hair? I mean, I know they were an admixed population themselves, not really pure Proto-North African or Basal Eurasian (not to mention they lived only around 15 KYA), but it does seem to suggest that looser hair may indeed have already developed either before or soon after “AMH” migrated out of Africa.

  6. The Tasmanian Aboriginals are/were the remnant of an early wave of migration into Australia, and the fact that they had tightly curled hair is suggestive that the trait is old, especially since the climate of Tasmania is not particularly tropical (or tropical at all), nor is that of southern Australia; it seems likely that their ancestors had the trait (of tightly curled hair) before migrating South to Tasmania (and likely also before, prior to arriving in southern Australia, and to Australia before that). Perhaps it could be that it was looser textured hair that developed more that once. It seems possible that later waves from South Asia into Australia, sharing looser hair mutations with peoples in South Asia (such as the ancestors of the Paniya and similar groups), may have introduced the looser hair trait.

  7. Edits:
    “…Tasmanian Aboriginals are/were the remnant of an early wave (the first or one of the first) of migration into Australia (as, as far as I know, the genetic evidence indicates that there was more than one prehistoric wave of modern human migration into Australia, and that modern mainland Aboriginals are the result of more than one wave of migration/more than one layer of admixture.)”

    “…seems possible that later waves from South Asia into Australia (post dating the first wave, the first wave likely being best represented by the Tasmanians and perhaps by certain tribes of the extreme south of the mainland)”.

  8. Edit: “…and perhaps also by certain tribes of the extreme south of the mainland, as in pockets of that region some tribes with an occurrence of Negrito-like traits including more tightly curled hair were at times reported)”.

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