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The Austronesian Explosion Was Crazier Than We Thought
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The Austronesian languages, credit

The Austronesian languages, credit

The Austronesians were crazy and extraordinary. Starting about ~5,000 years ago they set off from the environs of Taiwan, and began to push outward. For ~30,000 years the people of Melanesia had defined the eastern edge of human habitation, but the Polynesian branch of the Austronesians blasted past that, going alway the way to Hawaii and Easter Island. At the other extreme the ancestors of the Malagasy settled Madagascar, and island which the peoples of Africa had not reached as of yet despite ~200,000 years of human habitation. We don’t know what was happening here, but it is hard to pinpoint particular cultural, environmental, or genetic forces which might result in these sorts of radical change in mores. Humans are conservative and cautious by nature. But our particular lineage of modern humans far less so than our forebears or cousins. After all we did make it Oceania and the Americas, while the others did not.

But a great unresolved question is contact with the Americas. There’s a lot of suggestive evidence, but no clincher. But two recent papers increase the probability considerably. Both are in Current Biology, Two ancient human genomes reveal Polynesian ancestry among the indigenous Botocudos of Brazil and Genome-wide Ancestry Patterns in Rapanui Suggest Pre-European Admixture with Native Americans. Alexander Kim has already reviewed the nuts & bolts of the first paper. Here’s the major finding: heretofore the reasonable assumption about these Polynesian remains in interior Brazil were the product of escaped slaves, but there is an 80-90% probability that they died before any such enslavement of Polynesians could have occurred. In fact both remains may be pre-Columbian!

Cite: Genome-wide Ancestry Patterns in Rapanui Suggest Pre-European Admixture with Native Americans

Cite: Genome-wide Ancestry Patterns in Rapanui Suggest Pre-European Admixture with Native Americans

The second paper has a somewhat more subtle result. The inhabitants of modern day Easter Island are descended in the main from the Polynesians who arrived from the west. This has long been known from classical genetics and non-genetic fields. There has also been suggestion of European and Amerindian admixture. Entirely reasonable in light of Easter Island being a possession of Chile, and 19th century migratory events. What these authors did is that by looking at the distribution of ancestry outcomes in the genomes of Easter Islanders, they inferred that the admixture with Amerindians far predated that with Europeans. The rationale here is simple: recent ancestry from divergent groups tends to exhibit patterns of long alternating blocks, due to a relatively small number of recombination events. In contrast older ancestry tends to be broken up by many recombination events over the generations, until deconvolution can’t separate the two elements and they fuse as one. As an example of the latter case modern day Europeans and South Asians are compound populations whose admixture dates of ~4,000 years or more makes it difficult to trivially deconvolute their ancestral components on a genome-wide scale (though ancient DNA from Mal’ta likely can help in the case of Europeans).

Figure 4 above shows the match of two demographic models with the empirical results. M2 is one where Mestizos from Chile bring European and Amerindian ancestry into the genomes of Easter Islanders. M1 is where there is an ancient Amerindian admixture, followed by a later European one. The solid lines show the predictions, while the points show the empirical results from the samples. It is clear visually that M1 fits the data. There are many short Amerindian blocks, evident of an old admixture, as opposed to more varied and longer European blocks. The rough dates for Amerindian ancestry admixture are in the range of 1300 to 1400 A.D., which match reasonably well with when Easter Island was settled.

These results are strong. Not definitive and probably not the last word, though more Easter Islander samples can end the debate of admixture at least. But they make us wonder how incredible human migrations have been over the past ~50,000 years! Ancient people were far more daring than we had imagined, and I think we need to reconsider what “crazy” exactly is in many ways.

 
• Category: Science • Tags: Admixture 
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  1. RossM says:

    Please review your dates. The French study uses dates BC and AD but you have taken them to be BP. For example, in the first line you state the exodus from Taiwan was around 3,ooo years ago. It was around 5,000 years ago.

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    • Replies: @Keolu
    ~8,000 (out of Taiwan) is my understanding :)
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  2. Razib, their M2 hypothesis isn’t “Mestizos from Chile bring European and Amerindian ancestry into the genomes of Easter Islanders. ” Their M2 posits two separate admixture events, an earlier one from Europeans, followed by a later one from unadmixed Native Americans.

    The pre-admixed Mestizo involvement is my hypothesis in the comments of Kim’s blog, the one which the authors didn’t address. But earlier studies of Eastern Polynesians (both uniparental on Rapa and autosomal / genealogical on Rapa Nui) concluded that most likely source of Native American admixture in the Eastern Polynesia were the activities of Peruvian slave raiders in the 1860s. The Peruvians are, of course, Mestizos, but this hasn’t been factored in in the present study. The NA haploblock lengths in Peru would likely correspond to the admixture in the 1500s, i.e. slightly (although not significantly) longer than what the authors observed (but they probably underestimated the sizes of NA haplo tracts due to their conservative approach used to assign NA / European block boundaries in a situation where unadmixed reference NA data are hard to come by). An extreme bottleneck of the 1870s (when the effective population size dropped to as low as 36 people) would, of course, make dating of the prior genetic events less reliable in the first place.

    Lastly, a minor point. In Chilean times (post-1888) the Rapa Nui native survivors were confined to a reservation and practiced endogamy approx. until 1965 when they were finally granted citizen rights. Thus the Chileans are a less likely source of admixture.

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  3. Keolu says:
    @RossM
    Please review your dates. The French study uses dates BC and AD but you have taken them to be BP. For example, in the first line you state the exodus from Taiwan was around 3,ooo years ago. It was around 5,000 years ago.

    ~8,000 (out of Taiwan) is my understanding :)

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  4. #2, no, “Note that model M2 also includes the case in which both admixture events occur at the same time” in any case, to eliminate the mestizo probability what you need to do is look at correlations of NA+european segments, since NA admixture in some mestizo populations occurred relatively early.

    i’ve emailed the corresponding authors and will update accordingly.

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  5. #5, right, of course they also rule out a scenario where admixture from “pure” Europeans and Native Americans would have occurred roughly at the same time. But that’s not how Mestizo admixture would look – in the latter model, the NA admixture would have been “old” but passed through the mostly-European founders rather then directly to the Polynesians. Yes, looking for NA+European vs. NA+Polynesian segments has a potential to resolve it. Another cool possibility is to try to find out the number of the non-Polynesian founders, and perhaps to deduce portions of their genotypes (if there were few contributing European / NA founders, as it is likely to be case, then even with a couple dozen genotypes at hand one would have sampled these founders many times over)

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  6. in the latter model, the NA admixture would have been “old” but passed through the mostly-European founders rather then directly to the Polynesians.

    actually, it depends. the model of old admixture you see in the caribbean may not be quite generalizable all across latin america, where indios were reckoned to be the majority down to the 18th century across huge swaths. so you’d have more continuous admixture, so long + medium + short blocks.

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    • Replies: @Keolu
    Great stuff Razib. I'm a huge fan of your work and everything Polynesian + genomics.

    1.) Are you aware of what they are using as a "Polynesian ancestral reference" for this project? AIMS? an array based approach I am assuming? and if so how many locations in the human genome are they using to make this claim with an (n=2).

    2.) To your knowledge has there been any interest (that you know of) in understanding human genetic variation in Polynesian populations using NGS (short read etc.)? and If so which PI's are pursuing these questions (potentially in the San Diego area)?

    Thanks,

    Keolu

  7. Of course, in the typical Peruvians, it’s a continuous admixture, with the potential for shorter blocks further diminished by the fact that they may be as high as 75% Amerinidian in origin. But the privileged classes of old Peru avoided interbreeding with the indigenous and lower-classes for much of the more recent history?

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  8. “But they make us wonder how incredible human migrations have been over the past ~50,000 years! Ancient people were far more daring than we had imagined, and I think we need to reconsider what “crazy” exactly is in many ways.”

    I’ve thought about this quite a bit. First, the main barrier to migration and travel has always been blockage by powerful peoples. The reason why the Greeks, Romans, and early medieval Europeans never reached China is that the intervening peoples (Arabs, Persians, and for Alexander, Sogdians or the like) didn’t want them to. It’s not an impossibly difficult trip otherwise, for someone who has the motivation to go (a second constraint: why go?).

    But second, we assume that ancient peoples were prudent and utilitarian and calculated the odds. There’s little reason to believe that. People have all kinds of motives for doing all kinds of things, including both religion and mere whim (the wild hair). There’s ample evidence of wild hairs in history and anthropology.

    Notably, high energy, high status young men without an institutional place in their own society (except as “youth”) cause a lot of trouble and don’t have much fun or opportunity. In society after society they have the custom of going adventuring, either voluntarily or as exiles.

    The Inuit migration from Asia to Greenland took about 300 years. Of course, flat maps exaggerate the distance, but it’s still ~3000 miles of extremely inhospitable terrain.

    A second major point is that every time new information (much less new classes of information like DNA) is found, all the stories have to be rewritten according to the new information. However, the new information is almost but not quite as incomplete as the previous information, and the new writeup will have to be rewritten as soon as there’s a new big find.

    There might be a way to theorize results more probabilistically, or just in terms what is possible and likely. This would require complex, multiple theories, however, which unless very well written up might they confuse people unbearably (not just journalists).

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  9. I would add that most adventures probably end badly, either with death or with retreat. The notable ones are especially those entering unpopulated or underpopulated territory (the arctic, Polynesia). A second example would be the Turko-Mongol migration by conquest / mercenary service.

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  10. Peripherally related: there’s considerable speculation of Shang-era contact betweem the peoples in China and those in the N Pacific coast down to Mexico (Olmec). This is hardly proven though, in my opinion, not ridiculous either. This doeesn’t mean that the Native American peoples were “Chinese” or descended from Chinese. The Shang themselves were barely Chinese, and the relevant people might not even have been Shang.

    Menzies book about later contact is not taken seriously to my knowledge.

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  11. Should this be all that surprising? Given how far Polynesians would have had to have traveled to reach Rapa Nui in the first place, why would they stop there?

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  12. Keolu says:
    @Razib Khan
    in the latter model, the NA admixture would have been “old” but passed through the mostly-European founders rather then directly to the Polynesians.

    actually, it depends. the model of old admixture you see in the caribbean may not be quite generalizable all across latin america, where indios were reckoned to be the majority down to the 18th century across huge swaths. so you'd have more continuous admixture, so long + medium + short blocks.

    Great stuff Razib. I’m a huge fan of your work and everything Polynesian + genomics.

    1.) Are you aware of what they are using as a “Polynesian ancestral reference” for this project? AIMS? an array based approach I am assuming? and if so how many locations in the human genome are they using to make this claim with an (n=2).

    2.) To your knowledge has there been any interest (that you know of) in understanding human genetic variation in Polynesian populations using NGS (short read etc.)? and If so which PI’s are pursuing these questions (potentially in the San Diego area)?

    Thanks,

    Keolu

    Read More
  13. #12, Polynesians have traveled very far to reach Easter Island, but their expansion was already losing steam by then; they haven’t expanded beyond ca. 1200 AD, and their long-distance canoe voyages e.g. to Hawaii stopped about at the same time or soon after. After thorough deforestation of Rapa Nui in the 1200s, the residents were even less likely to explore far. In any case the latter phase of the Austronesian expansion was limited to un-populated islands? Australia has been bypassed by the expansion completely. I would hypothesize that scarcity of remaining un-populated dry-lands (getting smaller in size / harder to reach) eventually discouraged Polynesians from further long-distance exploration. If you keep sending young explorers far out in search of new habitable lands, but they don’t bring good news anymore, then eventually you just may stop trying, and the skills die out.

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  14. #14 – There’s a difference between settlement and exploration though. Polynesians may not have settled in Australia, but their dogs share a common origin in SE Asia with Australian dingoes.

    http://rspb.royalsocietypublishing.org/content/early/2011/09/06/rspb.2011.1395.full

    The genomes of sweet potatoes and coconuts both offer evidence of contact between Polynesians and South America.

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  15. #15 Of course some explorers might have failed in their quest to find habitable lands, yet perhaps succeeded in spreading plants or animals. But whatever geographic routes and technical means led to the dispersal of dogs, and sweet potato, across the South Seas, it remains irrelevant to the observation of Moreno-Mayar et al cited above by Razib, because they happened many centuries or thousands years before the controversial Amerindian admixture on Rapa Nui.

    The dogs are attested in Australia for nearly 4 millennia. Sweet potato is documented in Eastern Central Polynesia since about 1000 AD, and its spread across the far reaches of of Eastern Polynesian expansion, from Hawaii to New Zealand (but not in the prehistoric Western Polynesia), indicates that the radiation of sweet potato cultivation must have started there soon after settling of the Marquesas in the 300s AD. This time frame overlaps with the epoch of the greatest Polynesian ocean exploration, and perhaps there is some credence to the idea that the Polynesians might have reached the Americas back then. But the Native American admixture in Rapa Nui is tentatively dated to a time period a millennium later, when long-distance Polynesian exploration has long ceased.

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  16. ohwilleke says: • Website

    I’ve recapped the evidence on Pre-Columbian contacts with the Americas in a recent blog post and another post here. A couple of key points:

    * Kumara, a domesticated food crop used by Austronesians with South American (possibly Peruvian origins) has been dated as present on the Cook Islands (in Oceania somewhat near New Zealand) ca. 1000 CE.

    * From around 900 CE to 1100 CE, the people who lived in what today is the Lambayeque region, about 800 kilometers (500 miles) north of Lima, Peru had genetic links to the contemporaneous populations of Ecuador, Colombia, Siberia, Taiwan and to the Ainu people of northern Japan. These people were practitioners of the Middle Sican culture. It is not clear to what extent this contact was Austronesian in origin. Timing wise, this is a better fit to the source of the kumara than the Easter Island admixture event or the Brazilian remains. But, while the Taiwanese genetics are a good match for the Austronesians, the Siberian and Ainu similarities are not.

    Some of the more important references for my analysis include:
    [1] Maanasa Raghavan, et al., “The genetic prehistory of the New World Arctic”, Science 29 August 2014: Vol. 345 no. 6200 DOI: 10.1126/science.1255832.
    [2] David Reich, et al., “Reconstructing Native American population history”, Nature 488, 370-374 (16 August 2012) doi: 10.1038/nature11258
    [3] Matthew C. Dulik, “Y-chromosome analysis reveals genetic divergence and new founding native lineages in Athapaskan- and Eskimoan- speaking populations”, PNAS (May 29, 2012) doi: 10.1073/pnas/1118760109
    [4] Erika Tamm, et al., “Beringian Standstill and Spread of Native American Founders”, PLOS One DO: 10.1381/journal.pone.0000829 (September 5, 2007).
    [5] Alessandro Achilli, “Reconciling migration models to the Americas with the variation of North American native mitogenomes”, 110 PNAS 35 (August 27, 2013) doi: 10.1073/pnas.1306290110
    [6] Zegura, et al., “High-Resolution SNPs and Microsatellite Haplotypes Point to a Single, Recent Entry of Native American Y Chromsomes into the Americas.”, Mol. Biol. Evol. (2004) 21(1):164-175 doi: 0.1093/molbev/msh009
    [7] Judith R. Kidd, et al., “SNPs and Haplotypes in Native American Populations”, Am J. Phys Anthropol. 146(4) 495-502 (Dec. 2011) doi: 10.1002/aipa/21560

    There is also an emerging possibility that the pre-Columbian high civilizations of the New World share far more of a common heritage than previously recognized. The chronology is not inconsistent with a shared origin for all of these cultures in the vicinity of Monroe, Louisiana ca. 3700 BCE to 2700 BCE, around the same time that Paloeskimos arrived in Arctic North America after a complete hiatus of contact between the Old World and the New World from the flooding of the Beringian land bridge to ca. 3500 BCE. Monroe, Louisiana is also where anyone exploring any major river system in North America would eventually end up. So, the possibility of almost all New World civilization having its cultural antecedents in a stray group of travelers from that era that left little or no genetic traces can’t be ruled out.

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  17. Isn’t the Peruvian Times link quite old, from Jan 8, 2009?
    And AFAICT the mtDNA claims in Shinoda’s publications aren’t as sensationalist?

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  18. Menzies “1421″ about “the Chinese discovery of America” is horrible in its argument, but as I remember he has scavenged up a lot of information about contacts across the Pacific.

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  19. Over on 23andme there was a Native New Zealander who claimed not to be a Maori, but descended from an older people who lived in New Zealand before the Maori arrived and largely killed them all off.

    She tested her mtDNA and was D1, not the more familiar Austronesian mtDNA lines. D1 is found in both Siberia and Native Americans…

    What do people make of that?!

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    • Replies: @Anonymous
    link? weird, but that story's supremely hard to buy.

    you may know that some ethnographers (and "ancient Celtic NZ" types today) make a big deal about light hair in supposedly non-european-admixed Polynesians. no big mystery here ... Melanesian blondism.
  20. Anonymous says: • Disclaimer
    @Paul Conroy
    Over on 23andme there was a Native New Zealander who claimed not to be a Maori, but descended from an older people who lived in New Zealand before the Maori arrived and largely killed them all off.

    She tested her mtDNA and was D1, not the more familiar Austronesian mtDNA lines. D1 is found in both Siberia and Native Americans...

    What do people make of that?!

    link? weird, but that story’s supremely hard to buy.

    you may know that some ethnographers (and “ancient Celtic NZ” types today) make a big deal about light hair in supposedly non-european-admixed Polynesians. no big mystery here … Melanesian blondism.

    Read More
  21. ohwilleke says: • Website

    “Isn’t the Peruvian Times link quite old, from Jan 8, 2009? And AFAICT the mtDNA claims in Shinoda’s publications aren’t as sensationalist?”

    I haven’t been able to get a hold of the full text of these publications. The Peruvian Times link was triggered by a more recent report that was more vague. The older story appeared to tell me more than what had changed with the recent story.

    @ Paul Conroy

    There was a wave of Maori v. Maori genocidal intertribal warfare when firearms were introduced to New Zealand very early after European contact, but the evidence from lack of megafauna extinction points strongly against previous human habitation. Forced to guess, D1 in New Zealand would most likely be from someone from Asia who married a sailor (Austronesian or Asian or European) who ended up settling in New Zealand a long time ago. If the individual does have deep Maori roots in NZ, they may be non-patriline, non-matriline roots only visible in autosomal DNA.

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  22. ohwilleke says: • Website

    Also re the NZ claim, this would require more than twenty generations of pre-literate genealogy to be preserved orally in an accurate manner, in addition to about fourteen generations of post-literate genealogy, to survive in memory to the present. The first literate king lists and biblical genealogies apparently derived from oral histories are iffy in accuracy, and for commoners even in literate pre-bureaucratic-state societies, genealogies are rarely kept in accurate forms for more than ten generations, even if naming practices may suggest somewhat deeper links.

    The notion that any oral tradition passed down to someone alive today in New Zealand about their origins more than 1000 years earlier would be accurate is very dubious.

    A more plausible possibility is an origin in a Maori tribe that was destroyed in Maori tribal warfare.

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  23. @Pertula,

    That’s interesting, the woman in question, does have blonde hair?!

    I can’t find the exact article I read, but through google I find her name is “Monica Matamua” and she is a member of the small tribe called “Ngāti Hotu”:

    http://en.wikipedia.org/wiki/Ng%C4%81ti_Hotu

    I can only find a reference to her possibly having B2 or B4, so I guess it’s possible that I mid-remembered?!

    Maybe my ApoE4 is finally kicking in??

    http://en.wikipedia.org/wiki/Apolipoprotein_E

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