By examining mitochondrial DNA sequences from 18 prehistoric canids from both Eurasia and the New World along with ones from 77 modern dogs, 49 wolves, four coyotes and three Chinese indigenous dogs, an international group of researchers reports in Science that modern dogs are related to canids from Europe. Further, they traced the timing of domestication to between 18,800 years and 32,100 years ago to the time of European hunter-gatherers.
The researchers, led by the University of California, Los Angeles' Robert Wayne, constructed a phylogenetic tree based on those prehistoric canids and modern dogs and wolves. Based on this, they note that three dog clades were sister clades to ancient European canids and that one clade was closely related to modern European wolves. This, they write, indicates a European origin for dogs rather than the Middle Eastern or Asian origins previously suggested.
"It's these ancient wolf populations, now extinct, probably residing in Europe, that are the direct ancestors of domestic dogs," Wayne tells NPR's All Things Considered.
He adds to the New Scientist that the forerunners of dogs may have followed ancient European hunter-gathers around and fed on the carcasses left behind from their hunts.
The University of Victoria's Susan Crockford, though, says that the timing proposed isn't right for domestication. "Genetics alone is not adequate for unraveling the whole story," she says to the New Scientist. "In my opinion, the context of what humans were doing at that time does not support the right ecological conditions for domestication."
According to NPR, Elaine Ostrander from the National Human Genome Research Institute says that as Wayne and his colleagues were able to include 18 ancient canids, they were "able to build a pretty good statistical argument." She adds, though, that the whole story of how dogs were domesticated isn't finished.
"And so I think there probably remain to be found various fossils and ancient DNA sequences to sequence that will certainly fill in pieces that we're missing," she says. "It's clear that some things were going on in the Middle East and China, but we haven't been able to sort of fit that whole story together yet."
The study did not include samples from ancient Middle Eastern or Chinese canids and had fewer modern samples from those regions, which Peter Savolainen from the Royal Institute of Technology in Stockholm tells Science's Elizabeth Pennisi is a flaw. "[It is] the same as if you wanted to do a study of the origins of humans and you didn't have a single sample from Africa," he says.
Chung-I Wu from the University of Chicago further points out to Pennisi that mitochondrial DNA, as it is passed from mother to daughter, only tells one part of the story.
Wayne tells the New Scientist that he and his colleagues hope to be able to draw on nuclear DNA from dogs in the future.