It’s been long recognized that the domesticated dog—known to many as man’s best friend—evolved from the wild wolf, but scientists are not clear as to when this might have occurred, and how many times. In a post last fall, we looked at the domestication of wild dogs approximately 15,000 years ago. But when did the ancestors of dogs evolve into the species we now know as Canis familiaris?
There are two main schools of thought. One theory, published last year in the journal Science, looked at the partial genetic profiles of 59 dogs from 3,000 to 14,000 years old, as well as the complete profile of an Irish dog from 4,800 years ago, and compared these sequences to hundreds of modern dogs. This data suggested that domesticated dogs actually arose twice in completely separate events, once in Asia and once in Europe.
However, a recent study published in Nature Communications suggests an alternate theory. This group studied two ancient German dogs, one 5,000 years old, and the other 7,000 years old. They combined these genetic sequences with those of the Irish dog used in the Science study, and compared them to the genetic makeup of 5,649 modern dogs and wolves. Based on the high degree of similarity between ancient and modern genetic signatures, their results conclude that dogs were domesticated from a now-extinct wolf population approximately 40,000 years ago, which then split into the European and Asian populations approximately 20,000 years ago.
Some interesting additional details came out of this study. While wolves are carnivores, dogs developed the ability to digest starches, making them more omnivorous than their ancestors. Living with agriculture-based human populations, this was a huge advantage, and this ability appears to have evolved at roughly the same time as it did for humans. Also interesting, unlike their 5,000 and 7,000 year-old ancestors, modern dogs have developed duplicate genes, allowing them more genetic flexibility.
So which of these two theories of canine domestication is correct? The researchers agree that the more recent study doesn’t preclude the possibility of a second domestication event; they simply don’t see evidence of such an event in their samples. Critics of this research point out that it doesn’t explain the huge divide between European and Asian subspecies, nor does it explain that while Europe and Asia were highly populated with dogs, the areas between were notably empty. Future research is planned to look at more ancient Asian dogs, more recent European samples—such as those from the time of the Roman Empire—and also American samples in a bid to narrow down the ‘where’ of domestication as well as the ‘when’.
Photo credit: Arne von Brill