Jul
26
2017

Although we know that dogs diverged from wolves some thousands of years ago and were subsequently domesticated by people, we don’t know exactly when or how it happened.

In 2016, a study added to the search for the origins of dog domestication by suggesting that dogs could have been domesticated independently in both Europe and Asia. A new study published on July 18 in Nature Communications pushes back against this idea, suggesting domestication happened before dogs split into two populations.

This study focused on the whole genome sequencing of two ancient dog samples as well as reanalyzing previous samples. The two new samples included one from the Early Neolithic site of Herxheim (referred to as HXH) that dated back about 7,000 years and a specimen found in Cherry Tree Cave (referred to as CTC) that dates back about 4,700 years. They reprocessed data from the Irish dog from Newgrange (referred to as NGD) that the 2016 study used to determine the split in dog populations.

The researchers analyzed the Neolithic dog remains against 5,649 modern canids including breed dogs, village dogs, and wolves. All three ancient samples were most similar to the modern European dogs although they also all shared a significant component with Southeast Asian dogs. While the 2016 study had identified NGD as an outlier, the most recent study has determined that both NGD and HXH have 70–80% modern European-like ancestry.

In addition, while the CTC specimen was more different from modern dogs, the genome sequencing showed that CTC likely directly descended from the population represented by HXH. Based on those findings, the researchers concluded they found strong evidence for genetic continuity from the Paleolithic to the Neolithic.

Genetic analysis led the researchers to estimate that European and Southeast Asian dogs diverged about 17,500–23,900 years ago and to place the wolf to dog split at between 36,900–41,500 years ago. The older estimate of the split in dog populations between European and Asian seems to negate the double domestication hypothesis.

In the 2016 study, researchers hypothesized that the split had happened 6,400–14,000 years ago and that genetics showed dogs in Asia had traveled to Europe with people. However, there is evidence of dog remains in both Europe at this point, which suggests that dogs were domesticated in Europe before the Asian breeds traveled to Europe. That led the researchers to conclude that it’s possible to distinct groups of dogs evolving from two different groups of wolves were domesticated independently.

The more recent study pushes the split back, suggesting that dogs came from the same wolf origins, were domesticated between 20,000–40,000 years ago and then split into the two different populations that we can trace today.

While the researchers felt they had narrowed the timing of domestication, the specimens they tested were neither old enough nor had a broad enough geographic distribution to pin down a suggested origin for domestication. They instead determined that a broader set of ancient samples, including those from Central and Southeast Asia and the Middle East will be crucial to further clarify details of dog domestication and evolution.

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