The ectodysplasin A receptor (EDAR) gene, which is also known as rs3827760; 370V/A (where the V and the A represent Valine and Alanine, two aminoacids) or 1540T/C (where T and C are two nucleotides Thymine and Cytosine respectively) has an impact on tooth shape, hair thickness, sweat glands, and milk production and breasts in women. It is also found almost exclusively in Asian and Native American populaitons. It is extremely rare in Africa and Europe who carry the "ancestral" variant the 370V. The derived or mutated allele, where the Alanine was replaced for Valine in the protein or Thymine for Cytosine in the DNA strand, is a "recent" mutation known as 370A.
I have posted about it, when I mentioned that an ancient Amerindian from Brazil, a the Lapa do Santo individual who died over 6,000 years ago, carried the ancestral variant. Which is odd, since his ancestors came from Asia, and the derived variant is predominant there. This variant is also predominant among current Native Americans.
The question is: How could he have the original ancestral unmutated version while the other natives have the derived version? What about the bottle necks and founder effects, the Beringian standstill and so forth? These "filters" are supposed to have narrowed down the genetic variability in America, only a few mtDNA and Y-Chromosome haplogroups managed to enter America. So, with these limiations, wouldn't we expect all ancient Native Americans to carry the mutated Asian variant with them into America?
Posth et al. (2018) were the first to point out this anomaly:
"EDAR gene Variant. Our data show that a variant in EDAR that affects tooth shape, hair follicles and thickness, sweat, and mammary gland ductal branching and that occurs at nearly 100% frequency in present day Native Americans and East Asians was not fixed in USR1, Anzick-1, a Brazil Lapa do Santo 9600 BP individual and a Brazil Laranjal 6700 BP individual, all of whom carry the ancestral allele. Thus, the derived allele rose in frequency in parallel in both East Asians and in Native Americans."
These ancient American remains mentioned by Posth are old: the USR1 baby was 11,500 years old, Anzic-1 ~12,900 years old, the Brazilian dates are given above.
Yet the derived (mutated) form was present in the ancient site of Los Rieles "(12.0 kya) from coastal Chile of South America." (source), and the same source states that the mutated form increased to a frequency of 90% by the Early Holocene in both East Asia and America (11.6 - 5.0 kya). Posth et al. give the Los Rieles site a younger age of 10.9 kya, and confirms it had a mutated variant (See the Table 7 in Posth's Supplementary Material with a site by site detail).
Posth explains this anomaly by suggesting that the derived EDAR was not yet fixed at that time and that it evolved later, in some kind of convergent evolution on both sides of the Pacific. Probably promoted by natural selection.
A newer paper by Xiaowei Mao et al., (2021) from which the following image was taken, discusses ancient remains from the Amur River region, it also mentions EDAR.
The image above is captioned "(B) Allele counts for adaptive mutations of EDAR V370A in Tianyuan, ancient populations in the Amur region, and recently published ancient northern East Asians (Yumin, Bianbian, Boshan, Xiaogao, and Xiaojingshan) (Yang et al., 2020) from 40–6 ka. Purple shading represents the period of the LGM. Dots represent genotype calls (blue, ancestral alleles; red, derived alleles; gray, missing alleles). The number at the top of the bar (separated by a comma) shows the allele coverage for the derived and ancestral allele, and the number in parentheses at the bottom of the bar shows the number of individuals included in that time column. Genotypes were called using a maximum-likelihood-based method (snpAD) that takes into account possible errors in the covered alleles."
The text adds that "here we show that mutation V370A in the EDAR gene appeared in all ancient East Asians (including AR19K), except for AR33K and Tianyuan, the only two individuals in our sample predating the LGM stadial in East Asia." So it was not present in the 34.3-32.4 cal BP AR33K specimen from the Amur River area or the older Tianyuan man (40 ky old). It developed later. Remember that it was not found in ancient Amerindians either.
The paper adds that "our direct observation demonstrated that this allele emerged as early as ∼19 ka, as observed in the AR19K individual (Figure 4B), providing an older and more accurate upper boundary for the allelic age estimate." Then it spreads quickly reaching 93.7% in Asia nowadays.
Prevous estimates from 2008 (online source) reported a later date of fixation of 370A, some 10,740 years ago, it also suggested that "370A was likely at high frequency before the colonization of the Americas 10,500–14,000 years ago. Thus, the high frequency of 370A in Native Americans is most likely due to positive selection prior to migrations from Asia to America."
These explanations suggest that the derived allele was already present in the people who populated America.
But why is it not found in the other old remains? Some would argue that the first people to reach America carried the ancestral and the derived variants, and that eventually the later replaced the former. I believe that these people came from a group that carried the Ancestral allele, so this places them before the LGM, say 30 or 40 kya. Then came the post LGM migration with the mutated allele and erased all of the previous original Americans.
Another explanation lies with the Australasians: A 2021 paper on the genetics ancient Asians reported that none of the 7 ancient Jomon samples (Jomon hunter-gatherers lived in Japan) dated to ~2500–800 BC carried the derived allele. The Jomon were assimilated by the a later wave of people who now make up the Japanese population. The Ainu of Northern Japan are realated to the Jomon, and these, in turn, seem to have reached Japan using a coastal route, linking them to Southeast Asian people like tue Taiwan aborigines (Ami, and Atayal) and the Igorot, all of which are Austronesian minorities. (source). This coastal migration from ASEAN to Japan could also link them with the Onge, who only carry the ancestral allele.
Could Onge-related people have carried the ancestral allele into America in a first peopling wave, and in the process leave their genetic imprint there?
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2025 by Austin Whittall ©
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