Dogs evolved from a wolf lineage that has since gone extinct, a study of canine DNA suggests.
Researchers have long assumed that dogs branched off from a still-living wolf species. Geneticists have combed the world looking for wolf populations that most closely resemble dogs genetically, and concluded that dogs originated in the Middle East or Southeast Asia. But fossils suggest Europe as the site of dog domestication.
Posted June 4 at arXiv.org, the new study finds that interbreeding between dogs and wolves after domestication has made wolves in certain locations seem more closely related to dogs than they actually are.
Adam Freedman of Harvard University and an international group of collaborators compared DNA from three breeds of dogs (a boxer, a Basenji and an Australian dingo) to that of three gray wolves (Canis lupus) from Croatia, China and Israel — three locations proposed as centers of dog domestication. All of the wolves were equally related to the dogs, indicating that none of them has a special claim to being the dog ancestor. The authors suggest that some other type of wolf, possibly an extinct species, produced the first Fido.
The researchers’ findings leave dog origins up in the air. “I agree with them that we should back off from setting a needle in the map” to indicate where dogs first appeared, says Mattias Jakobsson, a population geneticist at Uppsala University in Sweden.
With additional data, the study also challenges a recent report that the rise of agriculture and the ability to digest starchy food may have triggered domestication. Freedman and his colleagues date dog domestication to about 15,000 years ago, well before the advent of agriculture.
The earlier study found that dogs carry extra copies of a gene called AMY2B, which produces an enzyme that breaks down starch, while wolves have only two copies (SN Online: 1/23/13). The new study, which is larger and includes more wolves and dog breeds, found that some wolves actually do have extra copies of the gene. Dingoes, which split off from other dogs 3,500 to 5,000 years ago, also have two copies and Siberian huskies have only three or four.
Freedman’s combined data make a case against carbohydrates playing a key role in taming canines, Jakobsson says. “To me it says starch wasn’t involved in the first domestication event.”
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