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paleoanthropology, genetics and evolution

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  • Of Jamestown and Neandertals

    Wed, 2013-05-01 16:07 -- John Hawks

    About why cannibalism is a widespread human behavior in times of stress, new evidence emerges from a trash pit at Colonial Jamestown: "Evidence of Cannibalism Found at Jamestown Site".

    It is unclear how the young girl died but she was probably dead already and even buried before being butchered. According to a letter written in 1625 by George Percy, president of Jamestown during the starvation period, the famine was so intense “thatt notheinge was Spared to mainteyne Lyfe and to doe those things which seame incredible, as to digge upp deade corpes outt of graves and to eate them.”

  • Coprolite microbial ecology

    Thu, 2013-02-28 00:25 -- John Hawks

    The advent of metagenomic analysis of microbial communities has led to some unexpected insights about human biology. These techniques have quietly been leading to new discoveries from old archaeological contexts. One example is Alan Cooper's work demonstrating long-term changes in oral microbiota from ancient dental calculus ("Tracing teeth troubles with fossil bacteria").

    Another is a recent paper from Cecil Lewis' lab, "Insights from characterizing extinct human gut microbiomes." [1]. The paper is open access in PLoS ONE. In it, Raul Tito and colleagues recover DNA data from ancient coprolites, from three archaeological sites in the Americas. As discussed in the paper, they obtain good data from a 1400-year-old site in Mexico. Those people, who lived near present-day Durango, were contemporaries of the classic Maya and Teotihuacanos. As such, their gut microbiomes may provide a really interesting picture of health and diet from a key period in the prehistory of the Americas.

    Coprolites may seem simple, but each represents a unique history of deposition and subsequent preservation. The microbial community may shift during the early stages of this history, and subsequent DNA damage may shift estimates of microbial abundances away from their true values. They found one of their sites appeared to preserve a good signal, while the others were degraded:

    Most striking, both Rio Zape coprolites exhibited a gut microbiome signature with similarities to the children from a rural African village with the exclusion of a sample of U.S. modern adult gut microbiomes (see Figure S4 for a heat map of these data and Figure S5 for the variability in the source proportion estimates). ZA04 also harbored similarities to non-human primate gut. The coprolites from Caserones and Hinds Cave showed little similarity to a gut microbiome environment. A portion of Caserones coprolite microbial community was similar to compost, which may be explained by the post-mortem gut serving as an organic bioreactor filled with carbon and nitrogen from decaying food detritus. The microbial community assignment for Hinds Cave failed to assign well to any source environment.

    From this, we can see that any interpretation of data from a sample of ancient coprolites must be cautious. We're generally interested in how microbial communities may have changed in ancient populations, particularly in response to other factors such as shifts in diet. But as yet it's not very clear what kinds of changes we should predict in association with diet or other changes. That makes it hard to develop a convincing test of a hypothesis.

    This paper is more of a proof of principle. And in its discussion, Tito and colleagues present different ways to explain the kinds of differences that they found in the ancient coprolite microbiota. To me, the most provocative hypothesis is that changes may have more to do with parasite load than diet:

    Information from Rio Zape also supports a current hypothesis about the composition of human microbiomes in traditional communities, potentially revealing an important aspect of the ancestral human microbiome. Spirochaetes are atypical of gut microbiomes in cosmopolitan communities. However, Treponema was reported by Filippo et al. [21] in their comparative study of modern microbiota in children from Europe and rural Africa. In their study, Treponema was observed in the rural African children but was absent in the European children. They hypothesized that the Treponema may enhance the hosts ability to extract nutrients from fibrous foods and may provide anti-inflammatory capability. They raise the hypothesis that microbiota coevolved with ancient diets and that changes in food production greatly impacted the intestinal microbiota. Treponema was also observed in the published rural data for Malawi and Venezuela [22]. The results from Rio Zape provide further support for Treponema as part of the rural human microbiome. Specifically, Treponema now is observed in four rural communities from different continents, three extant communities and one community that has been extinct for over a thousand years.

    As we uncover more comparative data from living people, we will begin to have a better picture of the covariates of microbial community structure. Today's oral bacterial populations in "cosmopolitan" post-industrial peoples are uncharacteristic of past variation. The gut microbiota of cosmopolitan peoples may be just as uncharacteristic. The diversity may have had great importance to ancient health, especially at key times when pathogens were spreading through post-agricultural populations.


    References

    Synopsis: 
    A look within the gut microbiota of ancient Americans
  • Mailbag: Boas and "unconventional models" of American prehistory

    Tue, 2012-03-06 11:30 -- John Hawks

    Re: Solutrean publicity blitz:

    Dear John,

    I normally have a soft spot for unconventional models of
    American prehistory. Boas's speculations about the Iroquois
    representing a northward back migration from South America always
    fascinated me as did his idea that Raven myths found there way from
    North America to Siberia. In contrast the thinking behind the
    Solutreah hypothesis strikes even me as unimpressive.

    It helps that Boas had some observations to go on!

    Hrdlicka impresses me, how he traveled around to investigate claims of Pleistocene man in the Americas. That's the spirit I like -- take the claims seriously, go there and investigate, and report whether the evidence is good or not. We have too much arm waving today.

  • A Solutrean publicity blitz

    Sat, 2012-03-03 14:48 -- John Hawks

    So....

    About all the "Solutrean Paleoindian" news this week...

    There is no new evidence, no revelation, no reason why other archaeologists should revisit this issue at this time. The news is free publicity for the release of a book.

    The book, by Dennis Stanford and Bruce Bradley, titled Across Atlantic Ice: The Origin of America's Clovis Culture. The book argues that ancient Europeans, carrying knowledge of the Upper Paleolithic Solutrean toolmaking tradition, voyaged across the icy North Atlantic around the time of the Last Glacial Maximum to establish a new population in the Americas.

    I've been out of town so it took me a while to figure out why all these newspapers were suddenly interested. None of the news outlets that employ knowledgeable science writers have jumped on this, for good reason. There's no news here except the book release. An exception is The Washington Post, which ran a long article featuring Stanford and Bradley's claims ("Radical theory of first Americans places Stone Age Europeans in Delmarva 20,000 years ago").

    At this point, somebody reputable needs to review this and give a serious account of the book's claims, because there's too much hype going around. I went to Amazon to see if there was a Kindle version of the book for me to review. But there isn't a Kindle edition. So I thought, OK, I'll order the hardback. But Amazon doesn't have it in stock.

    In other words, the University of California Press publicity machine has done its job.

    I want to give some links to some other recent books about Paleoindians. I will be reviewing and reading several of these as I go through Stanford and Bradley's book. That won't be until after the AAPA meetings, because the hardback of Across Atlantic Ice will take a long time to get here, so if you want to learn more about the initial inhabitants of the Americas, I suggest looking at one or more of these. All are published after 2000, but the older ones are showing their age. I include them because the authors, including Dillehay and Crawford, are experts with their own views that merit comparison. Slightly older volumes are more likely to be found in libraries, also, and comparing them can be a useful reminder that the evidence about early New World peoples really does continue to change.

    I'm sure there are other books by specialists that I have missed, and I'll be happy to update.

    UPDATE (2012-03-08): A reader writes with another suggestion:

    Another writes to note that the publicity for Across Atlantic Ice has been mostly generated by the Smithsonian, owing to Stanford's position there, rather than University of California Press.

    Synopsis: 
    Hype over claims that American Indians came from Ice Age Europe
  • 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. The Peopling of the Aleutians. Science. 2012;335(6065):158 - 161.
    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.

  • 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.

  • 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.

  • 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.

  • 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

    Synopsis: 
    A news article on the genomics of Puerto Rican descendants of Taino peoples runs into hot water.

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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.