Hours after Joseph Pickrell put his genome on the internet, an anonymous blogger took the data and concluded that he came from Ashkenazi Jewish stock. Pickrell, a genetics graduate student at the University of Chicago, Illinois, was sceptical about the claim. But after talking to relatives, he discovered that he had a Jewish great-grandfather who had moved to the United States from Poland at the turn of the nineteenth century. "It was a part of my ancestry I was totally unaware of," he says. The blogger, who writes under the pseudonym Dienekes Pontikos at http://dodecad.blogspot.com/ [blogspot.com] had commandeered Pickrell's DNA as part of the Dodecad Ancestry Project, an ambitious project in which cutting-edge genomic analysis meets Web 2.0. Pontikos analyses genetic data submitted by followers of his blog to reconstruct personal ancestry and human population history — and reports his findings online. He is part of a small but growing group of 'genome bloggers', a mix of professional scientists and hobbyists proving that widely available tools for computational biology could enable recreational bioinformaticians to make new discoveries. "They are not amateurs. They are far from being amateurs," says Doron Behar, a population geneticist at Rambam Health Care Campus in Haifa, Israel, who studies human history. "I cannot stress enough the level of appreciation I have for their efforts." Pontikos has so far analysed several hundred thousand single-letter DNA variations from more than 2,200 individuals. That includes more than 200 submitted to him by readers of his blog, who had had their genomes analysed by genetics testing firms such as 23AndMe, based in Mountain View, California, with the remainder coming from publicly available datasets. The readers volunteering their genomes (identities stay private) are mostly keen to delve into their own ancestry. But Pontikos, who is from Greece and describes himself as an "anthropology dilettante", is more interested in unfurling the history of populations that tend to be overlooked by human-population geneticists. For instance, his analysis of genomes from people living in northern Eurasia reveals a genetic connection between populations in northern Finland and central Siberia (see 'Meet the ancestors'). David Wesolowski, a 31-year-old Australian who runs the Eurogenes ancestry project (http://bga101.blogspot.com), also focuses on understudied populations. "It's a response, in a way, to the lack of formal work that's been done in certain areas, so we're doing it ourselves," he says. Wesolowski and a colleague have drilled into the population history of people living in Iran and eastern Turkey who identify as descendants of ancient Assyrians, and who sent their DNA for analysis. Preliminary findings suggest their ancestors may have once mixed with local Jewish populations, and Wesolowski plans to submit these results to a peer-reviewed journal. But Pontikos sees little point in formally publishing his findings. "I can bypass them entirely, and have the entire world review what I write," he wrote in an e-mail. Indeed, comments on his blog — "could you please provide the eigenvalues for the principal component analysis", for instance — read like the niggling recommendations of a manuscript reviewer. ...