Dogs have long been our animal BFFs, but how far back can our companionship be traced? According to a new study, further back than we thought.

Previous studies have suggested that dogs became domesticated roughly 11,0000 to 16,000 years ago as companions to hunter-gatherers. But a new study published in Current Biology found that dogs were likely domesticated a staggering 27,000 to 40,000 years ago. Using the genome of a 35,000-year-old wolf, the researchers attempted to distinguish when exactly dogs split from wolves.

The remains used for testing—a rib found trapped in ice on Russia’s Taimyr Peninsula—likely belonged to a wolf that roamed the Eurasian steppe tundra during the Ice Age. Researchers compared the DNA of this ancient canine to that of contemporary wolves and dogs, then used an assumed rate of mutation to estimate when dogs broke off from wolves. 

Swedish Museum of Natural History geneticist Love Dalén says that the rate of mutation was much slower than originally expected, meaning that domestication had to have happened much earlier. "One scenario is that wolves started following humans around and domesticated themselves," she told the BBC. "Another is that early humans simply caught wolf cubs and kept them as pets, and this gradually led to these wild wolves being domesticated.”

[h/t: Yahoo.com, Quartz.com]