A dog skull found in a cave in Siberia is more than 30,000 years old, suggesting man’s best friend has been so for over twice as long as previously thought.

University of Arizona professor Gregory Hodgins used an accelerator mass spectrometer to measure the amount of radioactive carbon remaining in the dog skull, and found that domestication was occurring back when Neanderthals in Europe and Siberia were still small-group hunter-gatherers.

"They are probably providing protection, companionship and perhaps helping on the hunt,” said Professor Hodgins. “And it's really interesting that this appears to have happened first out of all human relationships with animals.”

The research paper is published in the peer-viewed PLoSOne.