john hawks weblog

paleoanthropology, genetics and evolution

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  • Aleut origins and relationships

    Sun, 2012-01-15 22:59 -- John Hawks

    Michael Balter last week had a news article in Science reviewing archaeological and genetic research into the origins and relationships of Aleut populations [1]. The topic has a rich combination of historical and contemporary approaches.

    Recent genetic work confirms the distinction: Mitochondrial DNA (mtDNA) from 69 of Hrdlička's skeletons showed that Neo-Aleuts, like most modern Aleuts, descend from a common ancestor that carried genetic markers known as haplogroup D, according to recent work by University of Utah geneticist Dennis O'Rourke. But most Paleo-Aleuts were members of haplogroup A, as are most groups now living in Arctic North America.

    Hrdlička argued that the Neo-Aleut populations came from the Alaskan mainland and replaced the Paleo-Aleuts. But Coltrain and others have found that the newcomers in fact coexisted with the original settlers. “The long-headed Paleo-Aleuts were still very much around” for several hundred more years, says anthropologist Richard Davis of Bryn Mawr College in Pennsylvania. About two-thirds of living Aleuts belong to haplogroup D and one-third to haplogroup A, according to work by Crawford and his co-workers, and they are presumed to be the result of admixture between Paleos and Neos. Crawford's research with modern Aleuts also suggests that they carry some Paleo-Aleut DNA, because their ancestors branched off from other Arctic peoples about 13,000 years ago—long before they colonized the islands, perhaps when they were still in Asia or Beringia.

    Such a great case, where today's scientists can draw upon Hrdlička's models of population history. Still, what I think we are seeing today is only halfway through a revolution in studying human population interactions. In this case, mtDNA haplogroup frequencies are fairly informative -- similar to the situation in the Neolithic of Europe. But as we move to whole-genome approaches, it will be possible to attain a much more refined understanding of the relationships and pattern of mixture between what look like distinct groups. Likewise, the distinction between long-headed and broad-headed populations radically oversimplifies what is possible from craniometric comparisons. The biggest limit on craniometrics and genetics is the availability of relevant comparative samples from other early Beringian and American populations. This situation is getting better for genetics, and anthropologists continue to find ways to expand our understanding of New World peopling. The Aleuts are not only an interesting group for their own distinctive history; their ancestry may give them a store of the variability that was present in Eastern Beringia before people moved further south into North America.

    The Aleutian islands are a microcosm of the human habitation of other, larger areas of the world. In my opinion, we aren't going to get the big areas right until we have approaches that work well in cases like this one.

    References

    1. Balter M. 2012. The Peopling of the Aleutians. Science 335:158 - 161.
    Tags: 
    America
    American Indians
    Alaska
    Aleut
    mtDNA
    craniometrics
    Ales Hrdlicka
    history of anthropology
    Synopsis: 
    A news article covers research into the history of Aleut populations.

  • Dusk monkeys

    Thu, 2011-12-01 08:59 -- John Hawks

    Donald Prothero on Skepticblog gives a history of one of the exceptional finds in the history of North American paleoanthropology: "A tooth, a myth, and creationist lies".

    When I visited the American Museum this fall to continue my research on fossil peccaries or javelinas (American pig-like creatures only distantly related to Old World pigs), I was keeping a close watch for one specimen in particular. Everyone who has fought in the evolution-creation wars has heard of it, and I wanted to finally see and touch the specimen for myself. It is the tooth that caused a sensation in the 1920s, and has since become something that creationists harp on excessively, even though their version of the story is full of lies and myths. It is the tooth known as Hesperopithecus haroldcooki (“Harold Cook’s western ape”).

    It's a story that everybody should know, if they don't already. It was an honest, and understandable mistake that should not have gone as far as it did. It was not ridiculous to think that an anthropoid primate might be found in Nebraska in the Miocene -- after all, there is a long Eocene record of primates in Wyoming, and there are anthropoid primates today in the Americas. But Henry Fairfield Osborn went to press with the claim before other specialists had the opportunity to inspect and verify it.

    The case is not alone in this quality -- a mistake goes to press and then other specialists shoot it down. That's what scientists do.

    Tags: 
    history of paleontology
    America
    Henry Fairfield Osborn

  • Mailbag: Denisovan in China and New World habitation

    Sun, 2011-11-06 14:11 -- John Hawks

    Re: "How widespread is Denisovan ancestry today?"

    Your website is so interesting I wish I were an anthropologist! The
    heat map showing interpolated spatial distribution of the frequency of
    Denisova alleles struck me - for a different reason than the subject
    of the article. Does this map add weight to the argument for a
    possible southern route for at least some of the peopling of the
    Americas? Or is it simply assumed that somehow all traces of these
    gene signatures would simply disappear during the migration from a
    northern route? I am trying to understand how this makes sense if the
    peopling of the Americas was exclusively a Northern route.

    Thanks for wonderful website.

    Not clear. The map is showing such a very small fraction of the overall genetic variation, that the similarity between the south China and central America region may be just noise. If I were to set about answering the question about New World habitation, I would start with a very different approach. Worth some consideration.

    Tags: 
    Denisova
    mailbag
    migration
    America
    China

  • A story behind Manis

    Tue, 2011-11-01 23:15 -- John Hawks

    A couple of weeks ago, I pointed to new research dating a mastodon kill site from Manis, Washington, to around 13,800 years ago ("Bone of the victim mastodon"). Today I ran across an interesting article in the Seattle Times that profiles the archaeologist who discovered the site, Carl Gustafson, and discusses why the Manis site became a focus of academic debate: "WSU prof was right: Mastodon weapon was older than thought, scientists say".

    What sets the story apart from the typical "maverick scientist against the establishment" theme is the candid admission that disseminating results is the standard by which we have to judge archaeology.

    Quentin Mackie, at the University of Victoria's Department of Anthropology, agreed the Clovis-first model most likely subjected Gustafson's site to unfair critiques. But over the years Gustafson, too, didn't share his results in a great number of high-profile journals.

    "I just think Carl was hiding his light under a bushel," Mackie said. "I respect what Carl did. He poured countless hours into documenting the site. But for the rest of us, we rely on publication of results in peer-reviewed journals, and I don't think his evidence was presented in a way that was persuasive enough. And I hate to say that."

    Gustafson concedes his output could have been greater.

    "I probably should have published more," Gustafson said. "But I had so much. I didn't know how to take all this information and make a story out of it."

    If you want your science to make an impact, you have to write more and write promptly. Science needs the details to get in front of more eyes.

    Tags: 
    metascience
    Clovis
    America
    open science

  • Potato sack race

    Fri, 2011-10-28 14:30 -- John Hawks

    Smithsonian magazine has a very nice article by Charles C. Mann, "How the Potato Changed the World", focusing on the effects of the Columbian exchange on Europe.

    “For the first time in the history of western Europe, a definitive solution had been found to the food problem,” the Belgian historian Christian Vandenbroeke concluded in the 1970s. By the end of the 18th century, potatoes had become in much of Europe what they were in the Andes—a staple. Roughly 40 percent of the Irish ate no solid food other than potatoes; the figure was between 10 percent and 30 percent in the Netherlands, Belgium, Prussia and perhaps Poland. Routine famine almost disappeared in potato country, a 2,000-mile band that stretched from Ireland in the west to Russia’s Ural Mountains in the east. At long last, the continent could produce its own dinner.

    When I toured through the Altai this summer, I was impressed at the healthy potato patch outside nearly every house. How unlikely it seems that this American crop should have become a central part of people's lives in some of the most remote parts of Central Asia.

    Tags: 
    agriculture
    domestication
    diet
    history
    America
    Europe

  • Watch who you call "extinct"!

    Wed, 2011-10-26 00:29 -- John Hawks

    Sometimes people wonder why human genetics projects should bother to involve anthropologists.

    From now on, this seems like a good example: "Rebuilding the genome of a hidden ethnicity".

    CORRECTED: This article originally stated that the Taíno were extinct, which is incorrect. Nature apologizes for the offence caused, and has corrected the text to better explain the research project described.

    The news article reports on a conference talk by Carlos Bustamante, who is working on the population genetics of the 1000 Genomes Project samples. The project includes whole-genome sequencing data from 70 research subjects from Puerto Rico, many of whom have a substantial fraction of ancestry from the native peoples of the Caribbean, chiefly Taíno. There are more than 4 million Puerto Ricans today, both on the island and throughout the United States, and their ancestry averages around 15% Native American. Genetically, that works out to 1.2 million copies of a typical gene derived from indigenous peoples, of course scattered in different ways across the genomes of Puerto Rican people today. That's a lot of information, and Bustamante and colleagues are using the information to test hypotheses about the ancestry and pattern of native ancestry in these people.

    The news coverage of the talk ran into trouble by describing the Taíno as an "extinct ethnicity". What happened next won't be a surprise to any anthropologist who works in the Caribbean. Over the course of a weekend, the comment section of the Nature news article was filled by people outraged at the description of their ancestors as "extinct". Many identified themselves as Taíno people, protesting an injustice.

    The communication failure here is obvious. A presentation that refers to descendants of an ancient population ought to use terms that are anthropologically valid. Here we have two words that provoked confusion and anger: "extinct" and "Taíno".

    "Extinct" just is not a term that should apply to the ancestors of living people. Whatever the dictionary may say, to an ordinary reader or listener, the closest association of "extinct" is probably "dinosaurs". Extinction without issue. Even when we refer to cultural practices, the term "extinct" invites confusion. Extinction implies a model of disappearance that is sudden and complete, which in many cultural contexts didn't happen.

    "Taíno" is a contested cultural category. A growing group of people today claim Taíno identity, not merely Taíno ancestry, who live on many Caribbean islands. Some cultural practices derived from pre-Columbian Taíno people are today still widespread, among people who may have no strong belief about their ancestors 500 years ago. The movement toward greater self-identification as Taíno has emerged within an international population. Any discussion of Taíno ancestry ought to be framed in terms of the living people today who have that ancestry. Some of them may have a small fraction of Taíno ancestry but still self-identify in that category; others have never self-identified in that way, a few of whom might even be horrified at the prospect.

    Genetic observations themselves have contributed greatly to the revival of the concept of Taíno identity. By demonstrating the high fraction of indigenous ancestry in Caribbean people, genetics has provided something more "real" to people than their cultural ties may seem. Past studies of admixture in the Caribbean were hailed by activists as "scientific proof" that the Taíno still exist. That is one of the anthropological problems: the geneticists are not neutral players in this social milieu, even if they have no commitment to any possible result.

    In my opinion, the 1000 Genomes Project participants are the good guys. The scientists directing the project have given a lot of thought to their selection of samples, funded workshops to discuss ethical issues that arise from sampling and analysis, and even came up with boilerplate language so that their hundreds of postdocs have a standard way refer to the different sample groups. The project has created tremendous value for those of us who study the range of human diversity and human origins.

    Some of the project scientists have worked to explain why it is important to encompass human diversity within large-scale sequencing projects (for example, a recent paper by Bustamante and colleagues [1]). Genetic studies of human populations have been strongly biased toward European populations, and secondarily toward populations from other parts of the world that are well-represented by immigrant communities within the United States and Western Europe. The bias means that we don't understand as much as we should about the relationship between genetics and health in other populations of the world. Rare variations, some of which contributed to disease risk or protection, are missed by our current samples -- even though in some cases more samples could be added at minimal cost.

    My point is that there are really good intentions behind the project, and from an NIH-centric perspective, the project attempted to be inclusive. But competing ideas of identity make human genetics a difficult area where miscommunication is inevitable. Categories that a human geneticist may think are perfectly clear, an anthropologist will tend to be more wary about.

    I saw the story on Gene Expression, where Razib Khan provides good commentary along the lines of my reactions. I would add that cases like this one add a deeper dimension to the usual kind of science miscommunication. People are sometimes very selective about the science they accept to believe. Probably in no cases are people so selective as when the outcome concerns their own identity.

    A great power of today's genetic technology is the opportunity it presents to allow people to discover their ancestry. But that power is easily twisted into a license to impose identity. When different groups have motives to construct genetic identity, then genetics becomes a powerful tool for each group to proselytize its particular version of cultural identity.

    Anthropologists are already engaged in this problem, in different parts of the world. Yet they are minor players. As we see in this article, the geneticists have large voices. Those voices are heard rapidly by activists of various kinds, who have extremely high levels of engagement with broader communities. Taíno and Nature are both obscure to most Americans, but within 72 hours one of those groups mobilized and forced a response from the other, in a way that will have a large impact on future scientific and news reporting.

    References

    1. Bustamante CD, Burchard EG, and De la Vega FM. 2011. Genomics for the world. Nature 475:163-5.
    Tags: 
    genomics
    1000 Genomes Project
    indigenous peoples
    American Indians
    America
    Puerto Rico
    Synopsis: 
    A news article on the genomics of Puerto Rican descendants of Taino peoples runs into hot water.

  • Bone of the victim mastodon

    Fri, 2011-10-21 20:37 -- John Hawks

    Michael Waters and colleagues [1] report on the date of a mastodon kill site from Manis, Washington. At 13,800 years old, it's not the earliest evidence of New World people, nor the only evidence of pre-Clovis hunting. I find it interesting because of the addition of genetics to the mix of evidence. The specimen is verified as a mastodon, and the bone used to kill it was itself made of mastodon bone:

    We also obtained high-resolution tandem mass spectrometry (MS/MS)–based protein sequences from the projectile point and rib, and used another mastodon sample as a second reference (tables S3 to S6). The MS/MS spectra from the bone point matched the reconstructed mastodon collagen sequences, with the highest scores being within a reference set of collagen sequences (table S7 and supporting table of bone point marker peptides). These results and controls show that the point was fashioned from mastodon bone.

    The conclusion of the paper suggests that the evidence of pre-Clovis megafauna hunting argues against a "blitzkrieg" scenario for megafaunal extinctions. Instead, the authors suggest that the extinction was staged over a period of nearly 2000 years. The invention of Clovis points around 13,000 years ago is proposed to be near the end of the process, which may have begun before 14,800 years ago according to a kill site at Hebior, Wisconsin.

    I think this distinction is just semantic. If 2000 years of human predation eliminated mastodons, mammoths, and all the rest of the megafauna, which occupied North America for more than a million years before that, it looks a lot like "blitzkrieg" to me.

    References

    1. Waters MR, Stafford TW, McDonald HG, Gustafson C, Rasmussen M, Cappellini E, Olsen JV, Szklarczyk D, Jensen LJ, Gilbert MTP, et al. 2011. Pre-Clovis Mastodon Hunting 13,800 Years Ago at the Manis Site, Washington. Science 334:351 - 353.
    Tags: 
    Clovis
    America
    North America
    American Indians
    hunting

  • "First Americans" article

    Tue, 2011-10-18 21:29 -- John Hawks

    Scientific American's November issue has a cover story on the peopling of the Americas, by Heather Pringle, and it has gone online for free: (UPDATE 2006-10-23: Well, that's strange. I read it for free at the link, but now it has gone to paywall. Rats.) "The First Americans: Mounting Evidence Prompts Researchers to Reconsider the Peopling of the New World". The article reviews several Clovis and pre-Clovis news stories from last spring, including some that I covered at the time ("Early New World archaeology news").

    Among the stories recounted is an attempt to redate the opening of the "ice-free corridor" between the Cordilleran and Laurentide ice sheets. The closure between these sheets has been argued to block overland migration into North America before Clovis times. Some geologists are now arguing for an earlier date.

    The big question now is whether the entire corridor lay open during this period, particularly the section to the north. Munyikwa thinks it did. His team recently dated sand dunes farther north, along the Alberta-Northwest Territory border, with similar results. These data, Munyikwa says, fit current thinking about the Laurentide ice sheet. The general consensus among geologists, he notes, “is that the ice sheet retreated in a northeasterly direction as a wide front, as opposed to [moving] in discrete lobes. We envisage that the deglaciated land extended to the north.” If so, explorers from Asia could have entered the corridor around 15,000 years ago, nearly 1,000 years after the route to the western coast opened.

    Not much on the genetics in the article, and now I think it will be interesting when ancient genomics reaches the New World.

    Tags: 
    America
    American Indians
    New World
    Clovis

  • Charles Mann interview

    Fri, 2011-09-02 09:53 -- John Hawks

    Razib Khan posts an interview with author Charles C. Mann, whose new book 1493: Uncovering the New World Columbus Created is an account of the social and ecological effects of the Columbian exchange on the peoples of the Americas.

    I knew that Asians had worked under brutal conditions on the railroads. But I had no idea that something like 250,000 Asian slaves had been taken to the Americas in the 19th century. Similarly, I suspect that most Mexicans don’t know that Mexico City had a thriving Chinatown by the early 1600s. And most Peruvians don’t know that Asians were a significant presence in Lima as early as the 1611 census. And so on.

    I liked his earlier book, 1491 a lot, and I'll be reading the new one soon.

    Tags: 
    books
    America
    American Indians
    history

  • "I would run screaming away"

    Thu, 2011-05-26 07:42 -- John Hawks

    This is such an incredible story about the "Clovis comet" hypothesis, I don't know where to start: "Comet Theory Comes Crashing to Earth".

    Oh, well how about we start with the fact that the idea's main exponent is living under an alias:

    Indeed, the team’s established scientists are so wedded to the theory they have opted to ignore the fact their colleague “Allen West” isn’t exactly who he says he is.

    West is Allen Whitt — who, in 2002, was fined by California and convicted for masquerading as a state-licensed geologist when he charged small-town officials fat fees for water studies. After completing probation in 2003 in San Bernardino County, he began work on the comet theory, legally adopting his new name in 2006 as he promoted it in a popular book. Only when questioned by this reporter last year did his co-authors learn his original identity and legal history. Since then, they have not disclosed it to the scientific community.

    Well, the whole thing was thoroughly vetted by the National Academy member who coauthored the paper, right?

    After the theory was first announced in 2007 in Acapulco, Mexico, [Vance] Holliday had attempted to collaborate with [NAS member James] Kennett to test the idea. But Kennett effectively blocked publication of the study last year after the results didn’t support the comet theory.

    Err...well...you certainly can't dispute the physical evidence, right? I mean, what about the high concentration of carbon spherules that were associated with the supposed impact?

    On March 25, Boslough reported that radio-carbon dating of a carbon spherule sample shows it is only about 200 years old — an “irregularity” that indicates is it not from the alleged 12,900-year-old impact time.

    This means that a sample from a layer purporting to show a high concentration of spherules at the inception of the Younger Dryas actually only was about as old as the Declaration of Independence.

    The article discusses whether the carbon spherules may have been deliberately "salted" into the samples by someone, presumably West/Whitt himself. The quote I pulled as the title of my post, "I would run screaming," comes from another geologist asked whether he would work with West on anything.

    This story has really unraveled into a geological version of Piltdown. Like Piltdown, there were many people who were outright skeptics from the start -- because the evidence just didn't make sense. And like Piltdown, there are true believers who will not give up even after the physical evidence is shown to be questionable, possibly doctored.

    Anyway, I've written about this several times:

    "A hard bolide to swallow?"

    "The Younger Dryas impact fizzle?"

    You can tell when I really think an idea is nonsense: all the blog post titles end with a question mark!

    Tags: 
    megafauna
    America
    metascience
    extinction
    American Indians
    Clovis
    impacts
    Synopsis: 
    The Clovis impact hypothesis runs off the rails as the strange background of its main proponent comes to light

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Neandertals

For years, I've worked on their bones. Now I'm working on their genes. Read more about the science studying these ancient people.

Denisova

From a finger bone of an ancient human came the record of a completely unexpected population. My lab is working on the science of the Denisova genome.

Acceleration

The advent of agriculture caused natural selection to speed up greatly in humans. We're uncovering some of the ways that populations have rapidly changed during the last 10,000 years.

Malapa

Just outside Johannesburg, the Malapa site is producing some of the most exciting finds in human evolution. This site is the headquarters of the Malapa Soft Tissue Project.