The tale of how grey wolves became the pet dog of today has received a new twist, with research suggesting our furry companions arose not just from one population of wild ancestors, but two.
Dogs were the first animals to be domesticated by humans, an event thought to have happened somewhere between 15,000 and 30,000 years ago when humans were living as hunter gatherers.
“Most other animals underwent domestication after the advent of agriculture,” said Dr Anders Bergström, first author of the research at the Francis Crick Institute. “I think it is a very fascinating thing that humans back in the ice age would have gone out and formed this relationship with this fierce predator.”
But how the process occurred remains unclear.
“We don’t know where it happened, what was the human group that did this, did it happen once or multiple times and so on,” said Bergström. “So it remains one of the big mysteries in human prehistory.”
The latest study is not the first to investigate the puzzle. Among previous work, a recent study suggested wolves were domesticated independently in Asia and Europe, but only the former contributed to the ancestry of modern dogs.
“A key finding of our study, in contrast, is that dogs have dual ancestry,” said Bergström.
Writing in the journal Nature, Bergström and colleagues report how they analysed 72 genomes from ancient wolves that lived in Europe, Siberia and North America up to 100,000 years ago, 66 of which were sequenced for the first time. The team compared these with genomes from early and modern dogs.
The results reveal that, overall, dogs are genetically most similar to ancient Siberian wolves, although these are not direct ancestors.
“It basically suggests that dogs would have undergone domestication somewhere in Asia,” said Bergström, although he said it is not possible to identify the location with precision.
But while the ancestry of some early dogs, such as those in Siberia, the Americas, east Asia and north-eastern Europe, appeared to be rooted solely in wolves from Asia, others, particularly those in Africa and the Middle East, and to a lesser extent Europe, were found to have an additional genetic contribution from a population of western grey wolves.
“The largest amount of this second source of ancestry is found in an ancient dog that is 7,000 years old, from Israel,” said Bergström.
What’s more, he said, contributions from this western population of wolves are seen in all modern dogs today – although it is greatest in those from the Middle East and Africa, such as the Basenji breed.
But questions remain. “We still can’t tell whether there were two independent domestication events followed by merging of those two populations, or if there was just a single domestication process, followed by mixing from wild wolves,” said Bergström, adding work remains to pin down the geographical origins of our canine companions.
“The search continues to narrow down exactly where dogs come from,” he said.
