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Ancient DNA Studies Tackle Aspects of Dog Domestication, Canine History

NEW YORK (GenomeWeb News) – New ancient DNA studies are refining researchers' views of canine history — from dog domestication to migration history in specific parts of the world.

In a PLOS One report published last night, for instance, researchers in Russia, Finland, Spain, and the US used targeted sequencing to assess DNA from a dog-like archaeological sample found in a cave in southern Siberia's Altai Mountains in the mid-1970s. Their results suggest that the ancient animal shared more genetic features with domestic dogs than with wolves, providing a new piece in the puzzle for those trying to retrace the timing and geography of dog domestication.

That team started from a 33,000 year-old skull sample from Razboinichya cave in the Altai Mountains that had a distinctly dog-like look about it. Just one older canine specimen sharing such morphological similarities with domestic dogs has been found so far, the 36,000-year-old Goyet dog from Belgium.

To determine whether the Altai dog resembles domestic dogs both physically and genetically, investigators extracted and sequenced DNA from tooth and from jawbone portions of the specimen, focusing on 413 nucleotides of sequence in the control region of the mitochondrial genome for each sample.

When they compared the identical tooth and jawbone sequences in the Altai samples with those from more than 140 other canines — including domestic dogs, wolves, coyotes, and other prehistoric canine samples — the researchers found evidence supporting the notion that the Altai dog is more genetically related to domestic dogs than to their wild wolf relatives.

The newly sequenced sample also differed at several sequence positions compared with Pleistocene wolf samples from the same Siberian cave, including some samples estimated to be far older than the Altai dog specimen.

The study's authors cautioned that it can be tricky to try to discern genetic relationships based on mitochondrial sequence data alone. Still, they explained, if the results hold up to further scrutiny they may help to more precisely pin down the timing and location of dog domestication.

"These results suggest a more ancient history of the dog outside of the Middle East or East Asia, previously suggested as centers of dog origin," University of California at Los Angeles ecology and evolutionary biology researcher Robert Wayne, the study's senior author, and his colleagues wrote.

"Additional discoveries of ancient dog-like remains are essential for further narrowing the time and region of origin for the domestic dog," they continued.

Meanwhile, an independent research team based in Australia, Argentina, and Chile used ancient DNA in its effort to untangle the mysterious history of the Falklands Islands wolf — the only terrestrial mammal known to have reached the islands, which are located nearly 286 miles east of Argentina.

The researchers sequenced stretches of nuclear and mitochondrial DNA from Falkland Islands wolf samples. They also assessed half a dozen ancient museum samples representing the fox-like Dusicyon avus, another now-extinct animal from mainland Argentina and Chile.

With this new genetic data in hand, the researchers put the divergence time between the Falkland Islands wolf and its closest canine relative — the American maned wolf — at roughly 16,000 years ago rather than at seven million years ago, as estimated in the past.

The more recent split suggests that the Falkland Islands wolf may have made its way to the islands when sea levels dipped dramatically around 19,000 to 26,000 years ago, the team explained online earlier this week in Nature Communications.

Further supporting that notion was the discovery of underwater terraces along a continental shelf off of Argentina that the study's authors believe could have decreased sea depths enough to allow formation of an ice bridge to the islands.

"At that time, there was a shallow and narrow … strait between the islands and the mainland, allowing the Falkland Islands wolf to cross when the sea was frozen over," senior author Alan Cooper, a researcher with the University of Adelaide's Australian Centre for Ancient DNA, explained in a statement, "probably while pursuing marine prey like seals or penguins."

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