He's been man's best friend for generations.
An ancient dog skull found in Siberia and dating back 33,000 years presents some of the oldest known evidence of dog domestication.
When combined with a similar find in Belgium, the two skulls indicate that the domestication of dogs by humans occurred repeatedly throughout early human history at different geographic locations -- rather than at a single domestication event, as previously believed.
"Both the Belgian find and the Siberian find are domesticated species based on morphological characteristics," said Greg Hodgins, a researcher at the University of Arizona's Accelerator Mass Spectrometry Laboratory and co-author of a study reporting the find.
"Essentially, wolves have long thin snouts and their teeth are not crowded, and domestication results in this shortening of the snout and widening of the jaws and crowding of the teeth."
The Altai Mountain skull is extraordinarily well preserved, Hodgins said, enabling scientists to make multiple measurements of the skull, teeth and mandibles that might not be possible on less well-preserved remains. "The argument that it is domesticated is pretty solid," he said. "What's interesting is that it doesn't appear to be an ancestor of modern dogs."
At 33,000 years old, neither the Belgian nor the Siberian domesticated lineages appear to have survived earth's last ice age. Still, they show, just how far back our special relationship with our canine companions goes, Hodgins said.
"The interesting thing is that typically we think of domestication as being cows, sheep and goats, things that produce food through meat or secondary agricultural products such as milk, cheese and wool and things like that," he said.
"Those are different relationships than humans may have with dogs. The dogs are not necessarily providing products or meat. They are probably providing protection, companionship and perhaps helping on the hunt."
"And it's really interesting that this appears to have happened first out of all human relationships with animals."