Anthropology

PNAS doi: 10.1073/pnas.1301760110 Evidence for deposition of 10 million tonnes of impact spherules across four continents 12,800 y ago James H. Wittke et al. Airbursts/impacts by a fragmented comet or asteroid have been proposed at the Younger Dryas onset (12.80 ± 0.15 ka) based on identification of an assemblage of impact-related proxies, including microspherules, nanodiamonds, and iridium. Distributed across four continents at the Younger Dryas boundary (YDB), spherule peaks have been independently confirmed in eight studies, but unconfirmed in two others, resulting in continued dispute about their occurrence, distribution, and origin. To further address this dispute and better identify YDB spherules, we present results from one of the largest spherule investigations ever undertaken regarding spherule geochemistry, morphologies, origins, and processes of formation. We investigated 18 sites across North America, Europe, and the Middle East, performing nearly 700 analyses on spherules using energy dispersive X-ray spectroscopy for geochemical analyses and scanning electron microscopy for surface microstructural characterization. Twelve locations rank among the world’s premier end-Pleistocene archaeological sites, where the YDB marks a hiatus in human occupation or major changes in site use. Our results are consistent with melting of sediments to temperatures >2,200 °C by the thermal radiation and air shocks produced by passage of an extraterrestrial object through the atmosphere; they are inconsistent with volcanic, cosmic, anthropogenic, lightning, or authigenic sources. We also produced spherules from wood in the laboratory at >1,730 °C, indicating that impact-related incineration of biomass may have contributed to spherule production. At 12.8 ka, an estimated 10 million tonnes of spherules were distributed across ?50 million square kilometers, similar to well-known impact strewnfields and consistent with a major cosmic impact event. Link

There was a recent article on the topic by Abdellaoui et al., and here is another one. Investigative Genetics 2013, 4:9 doi:10.1186/2041-2223-4-9 Clinal distribution of human genomic diversity across the Netherlands despite archaeological evidence for genetic discontinuities in Dutch population history Oscar Lao et al. Abstract (provisional) Background The presence of a southeast to northwest gradient across Europe in human genetic diversity is a well-established observation and has recently been confirmed by genome-wide single nucleotide polymorphism (SNP) data. This pattern is traditionally explained by major prehistoric human migration events in Palaeolithic and Neolithic times. Here, we investigate whether (similar) spatial patterns in human genomic diversity also occur on a micro-geographic scale within Europe, such as in the Netherlands, and if so, whether these patterns could also be explained by more recent demographic events, such as those that occurred in Dutch population history. Methods We newly collected data on a total of 999 Dutch individuals sampled at 54 sites across the country at 443,816 autosomal SNPs using the Genome-Wide Human SNP Array 5.0 (Affymetrix). We studied the individual genetic relationships by means of classical multidimensional scaling (MDS) using different genetic distance matrices, spatial ancestry analysis (SPA), and ADMIXTURE software. We further performed dedicated analyses to search for spatial patterns in the genomic variation and conducted simulations (SPLATCHE2) to provide a historical interpretation of the observed spatial patterns. Results We detected a subtle but clearly noticeable genomic population substructure in the Dutch population, allowing differentiation of a north-eastern, central-western, central-northern and a southern group. Furthermore, we observed a statistically significant southeast to northwest cline in the distribution of genomic diversity across the Netherlands, similar to earlier findings from across Europe. Simulation analyses indicate that this genomic gradient could similarly be caused by ancient as well as by the more recent events in Dutch history. Conclusions Considering the strong archaeological evidence for genetic discontinuity in the Netherlands, we interpret the observed clinal pattern of genomic diversity as being caused by recent rather than ancient events in Dutch population history. We therefore suggest that future human population genetic studies pay more attention to recent demographic history in interpreting genetic clines. Furthermore, our study demonstrates that genetic population substructure is detectable on a small geographic scale in Europe despite recent demographic events, a finding we consider potentially relevant for future epidemiological and forensic studies. Link

This is a nice little review of the state of the art in germline mutation rate estimation in humans. This was previously estimated using paleontological calibrations (especially the human/chimp split), but a slower mutation rate emerged on the basis of whole genome data from humans. There may be problems with the latter (because of false positive/negative mutations using whole genome sequencing), but the problem is an important one due to the use of the mutation rate to estimate time depth of common ancestry. In any case, the table on the left summarizes the results of several studies on the topic. Trends in Genetics, 17 May 2013 doi:10.1016/j.tig.2013.04.005 Properties and rates of germline mutations in humans Catarina D. Campbell, Evan E. EichlerSee Affiliations Summary All genetic variation arises via new mutations; therefore, determining the rate and biases for different classes of mutation is essential for understanding the genetics of human disease and evolution. Decades of mutation rate analyses have focused on a relatively small number of loci because of technical limitations. However, advances in sequencing technology have allowed for empirical assessments of genome-wide rates of mutation. Recent studies have shown that 76% of new mutations originate in the paternal lineage and provide unequivocal evidence for an increase in mutation with paternal age. Although most analyses have focused on single nucleotide variants (SNVs), studies have begun to provide insight into the mutation rate for other classes of variation, including copy number variants (CNVs), microsatellites, and mobile element insertions (MEIs). Here, we review the genome-wide analyses for the mutation rate of several types of variants and suggest areas for future research. Link

Most graduate programs in anthropology require us to take a course in methods to prepare us to “do anthropology” on our own. In class, we discuss what makes a good research question, the trade-offs between qualitative and quantitative data, and the importance of taking good field notes. Sometimes we even get to conduct research and experience firsthand how to enter a community, recruit informants, transcribe interviews, and code data. This practical training allows us to try out the methods we are learning in class and troubleshoot any problems we have along the way with our professors and peers. In this post, I want to talk about the benefits of this model for cultivating a related, necessary, but often neglected skill-set in graduate school – digital literacy. Digital literacy is loosely defined as the ability to understand and use a range of digital technologies. For an anthropologist, these are specific tools such as social media, digital repositories, or web design that can significantly augment our success as scholars. Most of us have heard about the benefits of using Twitter or have figured out how to post lecture slides onto our online course management systems. However, I have found from personal experience that it is not enough to know that these tools exist – we also need to understand and navigate the complex digital cultures which they (and we) are bound up in. I mentioned in my previous post that I am a fellow in the Cultural Heritage Informatics (CHI) Program at Michigan State University. The purpose of this fellowship is for graduate students to gain hands on experience with a range of digital tools which can improve our teaching, research and professional networking. However, the value from these experiences comes from the fact that they are contextualized within broader discussions relevant to anthropology today. Examples include creating a digital article and understanding the controversy over open access publications; developing a mobile app for archaeologists and figuring out how to incorporate this technology into ones fieldwork; or designing a digital archive and discussing the importance of persevering and increasing access to large bodies of data. During my time in CHI, I realized that each of these technologies comes with its own set of social and technical rules that are important to consider long before we can expect to become great tweeters,  online instructors, and anthropologists. For me, having a safe and structured space to experiment with these tools was an important part of realizing this. When I made a mistake, felt overwhelmed, or was just plain clueless about where to start – I had a support system to work through it and get the most out of the digital tools I was using. Although I can’t share every lesson I learned this year in one post, the following are a few examples of common misconceptions I and others have had about what it means to be a digitally literate anthropologist. Digital Identity – in a world where most search committees will Google you before they hire you, learning how to manage you digital identity is an indispensable skill. It’s not just about removing all those questionable Facebook photos, but also making sure to put your best face forward on all social media outlets. However, figuring out how to do this effectively can take time. It is unlikely that by simply creating a website or a Twitter account that you will immediately reap its benefits. It would be like walking to your field site and assuming your participants are going to scream the answers to your research questions at you (wouldn’t that be great!) Social media has its own weird culture – take a few weeks to learn and observe before you ever open your mouth (or start blogging/tweeting). Also, make sure to ask your colleagues for constructive feedback about your blog, tweets, website, etc. so you know how others perceive your digital presence. For more information on how to manage your online academic identity

The semester is over and grades are in. My family just moved to a bigger place — one block down the street, actually — thanks to my wife’s tenure promotion. And the stress of the two combined, plus Herculean applications of caffeine and alcohol (I thought they were supposed to cancel each other out, no?) has got me nursing a stubborn infection. While I convalesce I am enjoying being reunited with my book collection, which has mostly been in boxes in the attic since 2007. Last night I picked up Frazer’s The Golden Bough, one of many texts I purchased in a fit of compulsive consumerism but never read, and have resolved to read things I enjoy this summer. What will you be reading now that classes are out?

For those interested in a more in-depth look at the state of Minoan/Mycenean script decipherment in the late 1940s, or more generally in the life of Alice Kober, here is a link to a wonderful digital collection of her papers, held at the University of Texas.  It’s neat stuff, giving a detailed look at the discipline just prior to the decipherment of Linear B, and involving correspondence with many of the luminaries of the age. Filed under: Linguistics

A very impressive data dump on Tibetan genetic variation gives us an excellent picture on both the Y-chromosome and mtDNA side. There are two interesting things about Tibetans -at least to me. First, their mtDNA is dominated by haplogroup M9, which is ~39 thousand years old, suggesting an early settlement after the dispersal of modern humans across Eurasia. Second, their Y-chromosomes are dominated by Y-haplogroup D, the sister clade of African haplogroup E, which links in some (unspecified, but I'm guessing old) time depth with such diverse peoples as the Andaman Islanders and the Ainu. Mongolians also share haplogroup D, but this is perhaps not surprising given the well-known links between Mongolia and Tibet. One might attribute the high Tibetan D frequency to drift, but drift acts randomly, and I don't think it's a coincidence that it acted in the same way in three quite different and fairly isolated corners of Eurasia to produce the Tibetan/Andaman/Ainu local peaks in an otherwise rather barren haplogroup D landscape. There are other interesting details, such as the presence of R1a*(xM17) in Tibet, a haplogroup that has a patchy distribution in Asia. In a sample size of ~2,354 it's possible to get one of these less successful relatives of mega-groups like R-M17, and their systematic study may help root in space the earliest history of these lineages. Mol Biol Evol (2013) doi: 10.1093/molbev/mst093 Genetic evidence of Paleolithic colonization and Neolithic expansion of modern humans on the Tibetan Plateau Xuebin Qi et al. Tibetans live on the highest plateau in the world, their current population size is nearly 5 million, and most of them live at an altitude exceeding 3,500 meters. Therefore, the Tibetan Plateau is a remarkable area for cultural and biological studies of human population history. However, the chronological profile of the Tibetan Plateau's colonization remains an unsolved question of human prehistory. To reconstruct the prehistoric colonization and demographic history of modern humans on the Tibetan Plateau, we systematically sampled 6,109 Tibetan individuals from 41 geographic populations across the entire region of the Tibetan Plateau and analyzed the phylogeographic patterns of both paternal (n = 2,354) and maternal (n = 6,109) lineages as well as genome-wide SNP markers (n = 50) in Tibetan populations. We found that there have been two distinct, major prehistoric migrations of modern humans into the Tibetan Plateau. The first migration was marked by ancient Tibetan genetic signatures dated to around 30,000 years ago, indicating that the initial peopling of the Tibetan Plateau by modern humans occurred during the Upper Paleolithic rather than Neolithic. We also found evidences for relatively young (only 7-10 thousand years old) shared Y chromosome and mitochondrial DNA haplotypes between Tibetans and Han Chinese, suggesting a second wave of migration during the early Neolithic. Collectively, the genetic data indicate that Tibetans have been adapted to a high altitude environment since initial colonization of the Tibetan Plateau in the early Upper Paleolithic, before the Last Glacial Maximum, followed by a rapid population expansion that coincided with the establishment of farming and yak pastoralism on the Plateau in the early Neolithic. Link

PNAS May 14, 2013 vol. 110 no. 20 8025-8029 doi: 10.1073/pnas.1301474110 Ash from the Toba supereruption in Lake Malawi shows no volcanic winter in East Africa at 75 ka Christine S. Lane et al. The most explosive volcanic event of the Quaternary was the eruption of Mt. Toba, Sumatra, 75,000 y ago, which produced voluminous ash deposits found across much of the Indian Ocean, Indian Peninsula, and South China Sea. A major climatic downturn observed within the Greenland ice cores has been attributed to the cooling effects of the ash and aerosols ejected during the eruption of the Youngest Toba Tuff (YTT). These events coincided roughly with a hypothesized human genetic bottleneck, when the number of our species in Africa may have been reduced to near extinction. Some have speculated that the demise of early modern humans at that time was due in part to a dramatic climate shift triggered by the supereruption. Others have argued that environmental conditions would not have been so severe to have su

Journal of Evolutionary Biology DOI: 10.1111/jeb.12107 Cultural and climatic changes shape the evolutionary history of the Uralic languages T Honkola et al. Quantitative phylogenetic methods have been used to study the evolutionary relationships and divergence times of biological species, and recently, these have also been applied to linguistic data to elucidate the evolutionary history of language families. In biology, the factors driving macroevolutionary processes are assumed to be either mainly biotic (the Red Queen model) or mainly abiotic (the Court Jester model) or a combination of both. The applicability of these models is assumed to depend on the temporal and spatial scale observed as biotic factors act on species divergence faster and in smaller spatial scale than the abiotic factors. Here, we used the Uralic language family to investigate whether both ‘biotic’ interactions (i.e. cultural interactions) and abiotic changes (i.e. climatic fluctuations) are also connected to language diver

A very exciting (and open access) new paper on Minoan mtDNA adds new ancient DNA data from the southeastern corner of Europe and from a critical period at the beginning of European history. The authors are able to reject Arthur Evans's idea that Minoan civilization had a North African origin, since North Africans bear the least similarity to the Minoans among the considered populations. Of course it's possible that Bronze Age North Africa had not yet experienced Sub-Saharan African gene flow -which probably accounts for its distinctiveness today (no African L mtDNA was found in the Minoan sample). On the other hand, the similarities between the Minoans and other ancient European mtDNA samples probably testifies to Minoans being indeed related to the Neolithic population of Europe. This is particularly interesting in the case of Minoan Crete, which may have been visited in pre-Neolithic times, but was permanently settled only during the Neolithic, thus minimizing the possibility of an inclusion of a