The story of how gray wolves became today’s companion dog has received a new twist, with research suggesting that our furry companions not only emerged from a population of wild ancestors, but from two.
Dogs were the first animals domesticated by humans, an event thought to have occurred between 15,000 and 30,000 years ago, when humans lived as hunter-gatherers.
“Most other animals suffered domestication after the advent of agriculture,” said Dr. Anders Bergström, first author of the research at the Francis Crick Institute. “I think it’s a very fascinating thing that humans in the ice age have come out and formed this relationship with this fierce predator.”
But it is unclear how the process came about.
“We don’t know where it happened, what was the human group that did this, whether it happened once or several times and so on,” Bergström said. “Therefore, it remains one of the great mysteries of human prehistory.”
The latest study is not the first to investigate the puzzle. Among previous work, a recent study suggested that wolves were independently domesticated in Asia and Europe, but only the former contributed to the ancestry of modern dogs.
“A key finding of our study, on the other hand, is that dogs have a double ancestry,” Bergström said.
Writing in the journal Nature, Bergström and colleagues report how they analyzed 72 ancient wolf genomes that lived in Europe, Siberia, and North America until 100,000 years ago, 66 of which were first sequenced. The team compared them to the genomes of early and modern dogs.
The results reveal that, in general, dogs are genetically more similar to the ancient Siberian wolves, although these are not direct ancestors.
“It basically suggests that the dogs would have been domesticated somewhere in Asia,” Bergström said, though he said it is not possible to identify the location accurately.
But while the ancestry of some early dogs, such as those from Siberia, America, East Asia, and Northeast Europe, seemed to be rooted only in wolves from Asia, others, especially the of Africa and the Middle East, and to a lesser extent, Europe, was found to have an additional genetic contribution from a population of western gray wolves.
“The largest amount of this second source of ancestry is found in a 7,000-year-old dog, from Israel,” Bergström said.
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In addition, he said, the contributions of this western wolf population are seen today in all modern dogs, although it is greater in those of the Middle East and Africa, such as the Basenji breed.
But questions remain. “We still can’t tell if there were two independent domestication events followed by the merger of these two populations, or if there was only a single domestication process, followed by the wild wolf mix,” Bergström said, and he added that there is still work to be done to determine the geographical origins of our canine companions.
“Research continues to narrow down exactly where dogs come from,” he said.