The peopling of the Americas

July 12, 2012 • 9:55 am

by Greg Mayer

The Americas were the last continents to be inhabited, and there has long been controversy about how and when it occurred. There is a general consensus that the earliest Americans arrived from northeastern Asia in the late Quaternary, but the exact peoples involved, the routes taken, when they arrived, and the modes of travel are all much debated. A paper by David Reich and colleagues, in press in Nature, presents evidence on one aspect of the question– did the first inhabitants arrive in one, or in more waves of migration? It has always seemed probable that the Eskimos, culturally and linguistically distinct from the American Indians to the south, and occurring on both sides of Bering Strait, represent a distinct migration, but were the more southern peoples the result of one, two, or more migrations?

Note that Na-Dene (green) and Eskimo-Aleut (red) derive in part from an Asian (black; Yoruba are African) ancestry separate from that of Amerind or First American (blue). (The Na-Dene and Eskimo-Aleut are not a single arrival from Asia; the Han Chinese are too genetically distant from east Siberian peoples to capture the ancestral source in this comparison.).
D Reich et al. Nature, in press, doi:10.1038/nature11258

Here’s the money quote from Reich et al.’s abstract:

[W]e assembled data from 52 Native American and 17 Siberian groups genotyped at 364,470 single nucleotide polymorphisms. Here we show that Native Americans descend from at least three streams of Asian gene flow. Most descend entirely from a single ancestral population that we call ‘First American’. However, speakers of Eskimo–Aleut languages from the Arctic inherit almost half their ancestry from a second stream of Asian gene flow, and the Na-Dene-speaking Chipewyan from Canada inherit roughly one-tenth of their ancestry from a third stream.

The three migrations thus were by 1) a group the authors call First American, that gave rise to almost all of the Indians of North and South America; 2) the Na-Dene, a group also linguistically identified, that occurs in the US Southwest and a few other places in the US and Canada; and 3) the Eskimo-Aleut, who arrived most recently. These three groups had also been identified by the late linguist Joseph Greenberg (who called the first group “Amerind’).

This is actually pretty much the story as I understood it from the viewpoint of a biologist paying casual attention to the anthropological results. Media accounts (NY Times, BBC) make it sound a bit more novel and controversial than I would have thought. This could be due to my not fully grasping the state of the debates within anthropology (quite possible!), or the hyping that tends to accompany reporting of even the best scientific work.

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Reich, D. et al. 2012. Reconstructing Native American population history. Nature, in press.

53 thoughts on “The peopling of the Americas

    1. Well, duh.

      (“Arthur J. Jelinek, an anthropologist who noted similarities between Solutrean and Clovis styles in a 1971 study, noted that the great geographical and temporal separation of the two cultures made a direct connection unlikely. He also noted that crossing the Atlantic with the technology of the time would have been difficult if not impossible,”)

  1. I was rereading Haldane’s “Inequality of Man” the other day – I like science history – but I noticed that he mentioned a significant incidence of blood group B among Tierra del Fuegians (a group otherwise absent in America, I seem to recall). Has that old result been disproved, or forgotten, or…

    1. Blood groups can be due to external selection, by disease, especially in a comparatively isolated group or with a virulent disease. The predominance of O in the Amerind population could be because other groups were more vulnerable to a specific disease. Likewise, the Bs in Fuegia might have been due to isolation from disease or because another disease was found there. (for example, in Ireland 47% of the population are O). The trouble is that Fuegians are extinct as far as I am aware, or there are not many left.

      There was the work of Walter Neves who claimed a Melanesian input from skulls in Brazil –
      Neves, WA; Prous A, González-José R, Kipnis R, Powell J.. “Early Holocene human skeletal remains from Santana do Riacho, Brazil: implications for the settlement of the New World.,”. J Hum Evol (2003 Jul 45(1):19-42)

      I think while there is always the possibility of a small one-off influx of say a boatload of people, but that might not leave much leagacy in the population as a whole (there is always the Founder effect though).

        1. Thanks, Dominic, I had not seen that particular one. I assume, with respect to this latest paper, even if it’s not there perhaps because ‘pure’ Dorset people DNA is unavailable, that the Dorset people were from among that earliest of the three major migrations.

          On a different note, I am given to believe that a Dorset living in the middle of the east coast of Greenland say,1500 years ago, who climbed to a very high point on an extraordinarily clear day and looked with excellent eyesight to the east, would be able to spy a high point on the west coast of the not yet humanly populated Iceland. With suitable conventions about Greenland being in America, which makes sense geologically, and Iceland being in Europe, which doesn’t, but does make sense culturally, the following would be a consequence:

          Despite myths about Columbus, and truths about the Vikings, it would have been someone from the America side of the Atlantic who spied Europe before any European spied the other side of Atlantic.

          I drove around Snaefjellsjokull, that Icelandic high westerly point, and it would be an easy walk to that summit if it weren’t for the possibility of crevasses; I think less than a kilometre on ice. Costs there are way less than 5 years ago, so I suppose getting a guide is feasible. But getting a day where you might see Greenland would be very lucky.

  2. Subscribing just because you mentioned Greenberg. His super-families are still controversial, and for good reason, but he did a lot of linguistics.

    And also this is something that has always interested me.

    As for the media accounts, I’m going with:

    “the hyping that tends to accompany reporting of even the best scientific work.”

    1. While it is technically true that Greenberg did a lot of linguistics, what I meant to type is that Greenberg did a lot for linguistics.

  3. ‘S OK – found it myself. Lipschutz (1946) determined that all the B came from European ancestry.

    1. Yes, possible (and as here, actual) introgressions. But if you look at the problems to establish Neanderthal and Denisovan introgression, they had a hard time resolve that out of possible bottlenecks.

      The process of coastal migration, and specifically its out-most tip, is nothing but a template for a history of serial bottlenecks.

  4. I worked in Native American genetic anthropology about 10 years ago and this basically confirms the hypothesis that we assumed at that time. Three primary migrations, with just enough admixture to make things uncertain. Well, not so uncertain anymore.

  5. And where stands the “Kennewick Man” find in all this? Now non-controversial? Skull still in scientific stasis, because of tribal religion?

    1. According to Wikipedia:

      “The remains are now at the Burke Museum at the University of Washington, where they were deposited in October 1998. The Burke Museum is the court appointed neutral repository for the remains and as such they are not on exhibition. They are still legally the property of the U.S. Army Corps of Engineers, as they were found on land under its custody.”

  6. Related to this, I’m currently reading “After The Ice Age: The Returun of Life to Glaciateed North America” by EC Pielou (1991, U Chicago(!) Press).

    Most interesting concerning why the glaciations come and go, refugia, and so forth. I’d be interested in hearing from anyone familiar with this one, if there’s a better volume on the same topic.

    1. Yes, that’s a very good book. Many of the questions it poses about migration routes, refugia, nunataks, etc. can now be addressed with fine level genetic data. Unfortunately, I’m not aware of any book that covers this. Some of John Avise’s books on phylogeography will have relevant material, but not focused on the formerly glaciated terrain.

      GCM

        1. Glad to have mentioned it! (Now if I can just get jac off the theology long enough to do the same.)

          You’ve probably already gotten to the part about the separate periodicities of variation in the angle of the axis of spin, the ellipticity of the orbit and the time of the closest approach to the sun. That really grabbed my attention.

      1. You might try: First Peoples in a New World: Colonizing Ice Age America by David J. Meltzer (2010). He has good summaries of the evidence to date on genetics, migration routes, linguistics, etc. on the peopling of the Americas. A good read.

  7. Pardon my serious lack of expertise, particularly if it’s already in the article or responses, but is it clear where the Dorset fit in here? My impression is that there may be still some Dorset people ancestry among people from islands just where Hudson Bay becomes James Bay, or was during the age of European exploration of the Arctic. I understand that the Inuit pretty well completely replaced the Dorset, but very recently compared to the 12,000 years or possibly much more that America (that is, the Americas, pace Monroe)has had humans.

      1. Sorry, this went the wrong place initially:

        Thanks, Dominic, I had not seen that particular one. I assume, with respect to this latest paper, even if it’s not there perhaps because ‘pure’ Dorset people DNA is unavailable, that the Dorset people were from among that earliest of the three major migrations.

        On a different note, I am given to believe that a Dorset living in the middle of the east coast of Greenland say,1500 years ago, who climbed to a very high point on an extraordinarily clear day and looked with excellent eyesight to the east, would be able to spy a high point on the west coast of the not yet humanly populated Iceland. With suitable conventions about Greenland being in America, which makes sense geologically, and Iceland being in Europe, which doesn’t, but does make sense culturally, the following would be a consequence:

        Despite myths about Columbus, and truths about the Vikings, it would have been someone from the America side of the Atlantic who spied Europe before any European spied the other side of Atlantic.

        I drove around Snaefjellsjokull, that Icelandic high westerly point, and it would be an easy walk to that summit if it weren’t for the possibility of crevasses; I think less than a kilometre on ice. Costs there are way less than 5 years ago, so I suppose getting a guide is feasible. But getting a day where you might see Greenland would be very lucky.

  8. It is a bit disappointing that they only looked at far northeast Asian candidates, and not candidates from farther south in Asia. The current northern Asian population might not always have been there.

  9. Excellent article. It is distracting, however, to be confronted with the common redundancy “general concensus” in the first sentence.

    1. Except it was “general consensus” …

      Why is this a redundancy? My reading of this is that the majority of opinion agrees about the general features of the theory, with some of the specifics still disputed.

      /@

        1. Well, if you’re going to accept dictionary definitions that literally, good luck to you! Perhaps we should continue conversing in lojban… 😉

          Another sense is “majority of opinion”, which is what I discussed above.

          /@

          1. Ah, but that wouldn’t be a consensus!

            But I figure there is another meaning of “general consensus”…. taking it to mean consensus on the majority of matters with dispute remaining on a few.

            1. Um… “consensus on the majority of matters with dispute remaining on a few” ≡ “the majority of opinion agrees about the general features of the theory, with some of the specifics still disputed” … no?

              /@

    2. Perhaps the author really meant: “Generally there is a consensus……, but a few particular people cling to believing in settlement of America (which should be the word for ‘the Americas’, again despite the doctrinal Monroe not the Hollywooden one) by European ice agers.” So “general” is there to indicate that some people, serious, or at least who take themselves that way, do not agree.

  10. No sign of the Lost Tribes of Israel there either! I wonder how the Mormons would respond to this? Probably close their eyes/ears and ignore it, I guess.

    1. Signs are already being prepared for the museum display, to the effect that “some people dispute this evidence”.

      1. +1!

        The Mormons would really care about this kind of study if only it revealed the names of the ancestors, so they could be properly baptized.

        Other than that, why should they have any interest in actual history?

  11. I had heard on a documentary that except for the current Inuit, all the indigeneous peoples of the Americas are from a split in central Asia on an east-west axis: some went west and became Europeans (eventually) and some bypassed where the ancestors of the Han were and went north and east and east and east and then eventually through the Americas. I wonder how that fares … what changed the view?

    1. DNA analysis, the main subject of this posting has changed/enhanced/enriched that view. The split you reference (european vs asian) is much older than when humans populated North America.

  12. In an amazing follow-up, one day later, we have this gem in Science today:
    Jenkins et al.: Clovis Age Western Stemmed Projectile Points and Human Coprolites at the Paisley Caves.

    -Which, using DNA in human coprolites from a cave (good old Paul Martin would have loved this, may he rest in peace), as well as flint artefacts, strongly suggests an earlier, fourth (or, as it were, first) wave of humans coming down into North America along the eastern coastline.

    Reported many places just now, e.g.
    http://www.newscientist.com/article/dn22053-was-america-first-colonised-by-two-cultures-at-once.html

    1. And in that article is a link to another article, “First Americans arrived 2500 years before we thought.”

      From the article.

      “The new hoard contains 15,528 items, the largest group of pre-Clovis stone objects ever found. It includes 56 well-preserved tools amongst many stone chips, flakes and fragments that probably broke off other tools.

      “What we have found is evidence of early human occupation dating back to 15,500 years ago, 2500 years older than Clovis,” says Michael Waters of Texas A&M University in College Station, lead author of the study.”

      ____

      “The team did not find enough organic matter at the site to pinpoint the age of the tools with radiocarbon dating. Instead they relied on a newer and slightly less accurate technique called optically stimulated luminescence, which uses light to free electrons trapped in minerals.”

      Very interesting. Need more data!

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