Dogs gradually evolved when European hunter-gatherers domesticated wolves more than 18,000 years ago, a new study suggests.
"We found that instead of recent wolves being closest to domestic dogs, ancient European wolves were directly related to them," said Robert Wayne, a professor of ecology and evolutionary biology in University of California, Los Angeles's College of Letters and Science and senior author of the research. "This brings the genetic record into agreement with the archaeological record. Europe is where the oldest dogs are found."
The scientists examined 10 ancient "wolf-like" animals and eight "dog-like" animals, most of which were from Europe, some more than 30,000 years old.
By comparing the mitochondrial DNA of the animals to those of 77 modern domestic dogs, 49 wolves and four coyotes, the scientists found that the domestic dogs were genetically grouped with ancient wolves or dogs from Europe.
That they were not grouped with wolves found anywhere else in the world or even modern European wolves led the researchers to a startling conclusion: dogs are derived from ancient European wolves that are now extinct.
According to Wayne, the wolves were probably first domesticated by hunter-gatherers.
"The wolf is the first domesticated species and the only large carnivore humans ever domesticated," Wayne said. "This always seemed odd to me. Other wild species were domesticated in association with the development of agriculture and then needed to exist in close proximity to humans."
Such a scenario would have been difficult for a large predator; however, Wayne noted, "one can imagine wolves first taking advantage of the carcasses that humans left behind -- a natural role for any large carnivore -- and then over time moving more closely into the human niche through a co-evolutionary process."
The theory of wolves following hunter-gatherers would also help explain the genetic divergence that led up to the appearance of dogs, since any wolves following migrating humans would have been pulled out of their native territory, making them less likely to reproduce with resident territorial wolves.
"This is not the end-story in the debate about dog domestication," he said, "but I think it is a powerful argument opposing other hypotheses of origin."