In this latest study, researchers radiocarbon-dated a Taimyr wolf bone they found in Siberia and concluded it to be about 35,000 years old. Researchers point to the ancient wolf as possibly the most recent common relative of modern wolves and dogs.
That means two things could have happened about 40,000 years ago, with the simplest scenario being that dogs became domesticated.
"The only other explanation is that there was a major divergence between two wolf populations at that time, and one of these populations subsequently gave rise to all modern wolves," study co-author Love Dalén of the Swedish Museum of Natural History said in a release.
Under that theory, the second wolf population would had to have gone extinct.
"It is [still] possible that a population of wolves remained relatively untamed but tracked human groups to a large degree, for a long time," study co-author Pontus Skoglund of Harvard Medical School and the Broad Institute said in a release.
Earlier work estimated genetic mutation rates that were much faster than what these researchers found. But the mutation rate in the Taimyr wolf genome was just half of what had been thought, Dalen told Reuters
"The difference between the earlier genetic studies and ours is that we can calibrate the rate of evolutionary change in dog and wolf genomes directly, and we find that the first separation of dog ancestors must have been in the older range," Skoglund told Reuters.
Another implication of this study: re-imagining how dogs became an important part of human society. As the BBC notes, a prevalent theory is that dogs became domestic creatures once humans settled into agricultural-based communities.
Humans could have also "caught wolf cubs and kept them as pets and this gradually led to these wild wolves being domesticated," Dalen told BBC. "If this model is correct, then dogs were domesticated by hunter gatherers that led a fairly nomadic lifestyle."