People and pooches may have struck up a lasting friendship after just one try, a new genetic study suggests.New data from ancient dogs indicates that dogs became distinct from wolves between 20,000 and 40,000 years ago, researchers report July 18 in Nature Communications.Dogs then formed genetically distinct eastern and western groups 17,000 to 24,000 years ago, the researchers calculate. That timing and other genetic data point to dogs being domesticated just once.That idea contrasts with a hypothesis put forward last year that dogs were domesticated separately in Europe and East Asia, with the Asian dogs eventually replacing the European mutts (SN: 7/9/16, p. 15). Scientists agree that dogs stem from wolves, but where, when and how many times dogs were domesticatedpassing down tameness and other traits over generationshas been rethought many times in the last few years (SN: 7/8/17, p. 20).The new study puts dog origins into one time and place again. Thats really important, says Peter Savolainen, an evolutionary geneticist at KTH Royal Institute of Technology in Stockholm who was not involved in either study. These new data indicate theres a single origin, and it wasnt in Europe, says Savolainen, a proponent of an East Asian origin of dogs.The new study examined the complete genetic blueprints, or genome, from a 7,000-year-old dog from Herxheim in Germany, and a 4,700-year-old dog from Cherry Tree Cave (also known as Kirshbaumhle) in Germany. The scientists also analyzed DNA data from a 4,800-year-old dog from Newgrange, Ireland, that had been described in the previous study positing two domestication events.A claim of multiple domestications for dogs requires extraordinary evidence, says study coauthor Krishna Veeramah, an evolutionary geneticist at Stony Brook University in New York. But complete genomes of the ancient dogs suggest a simpler story. We can explain all of our data just using one domestication event, Veeramah says.Although Veeramah and colleagues see a split between eastern and western dogs, that split probably happened after domestication took place. Modern European dogs still share heritage with Stone Age canines on the continent, hinting that all the pups came from a common source rather than separately domesticated Asian dogs replacing their European counterparts.These new data dont completely rule out multiple domestications (the single event is just the simpler explanation), nor do they indicate where humans and canines became BFFs, Veeramah says. A family tree constructed from the DNA data puts todays Southeast Asian breeds on the earliest branch, implying an origin in Asia. But a dog breeds present-day location may not reflect where dogs were actually domesticated more than 20,000 years ago, Veeramah says. The team that proposed double domestication is not convinced of a single origin. The new study is based on genetic data alone and doesnt take archaeological evidence into account, says Greger Larson, an evolutionary geneticist at the University of Oxford.Theres no smoking gun here, and theres no direct contradiction, says Larson. Our hypothesis of a dual origin remains a possibility, as does a single origin. Researchers wont know for sure until theyve analyzed older dogs from multiple places.The ancient doggy data also challenge a recently proposed idea that dogs were domesticated when early mongrels developed the ability to digest starch better than wolves could (SN Online: 1/23/13), allowing them to eat grains in early farmers trash heaps. A previous study found that todays dogs have many copies of the AMY2B gene, which produces an enzyme that helps break down starch, while wolves have only two copies.The new study finds that both ancient German dogs had two copies of AMY2B, while the Newgrange dog had three. Since those dogs lived thousands of years after domestication, the findings suggest the first domesticated dogs were no better equipped to digest starch than wolves were. But the ancient dogs do have other genetic variants that made it possible for the amylase gene to be copied later, Veeramah says. Exactly when that happened isnt clear.SEE ALSO:These genes could be why dogs are so friendlyJoin the conversation about this storyNOW WATCH: See how geologists scoop molten-hot lava into a bucket for testing
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