Dogs have been companions to humans for many millennia, but exactly when this relationship started is highly debated among scientists.
A study published this week in the Proceedings of the National Academy of Sciences reveals that canine domestication may have first occurred in Siberia 23,000 years ago when humans and wolves were isolated together during the Last Glacial Maximum. After this initial domestication event, dogs most likely followed humans when they migrated across the Bering Land Bridge from East Asia to the Americas 15,000 years ago, reports Megan Marples for CNN.
"Wolves likely learned that scavenging from humans regularly was an easy free meal, while humans allowed this to happen so long as wolves were not aggressive or threatening," Angela Perri, an archaeologist at Durham University and lead author of the study tells CNN.
The study was brought to fruition after Perri and her co-authors—David Meltzer, an archeologist at Southern Methodist University, and Gregor Larson, a scientist from Oxford University—were brainstorming how DNA evidence tells the story of migrating humans and dogs, reports James Gorman for the New York Times. After the authors scribbled down ideas on a whiteboard, they saw that both humans and canines had similar migration patterns and divergence that could explain how dogs and humans began their bond, reports the New York Times.
To see if the similarities between the timelines linked up with archeological evidence, Perri and her team analyzed the genome of 200 ancient dogs from around the world. They found that the canines had one genetic signature, A2b, in common. Once they reached the New World 15,000 years ago, they dispersed into four groups, reports David Grimm for Science.
The researchers found this dispersal matched a similar migration pattern of ancestral Native Americans that descended from Northern Siberia about 21,000 years ago. Connecting these timeline events between humans and dogs, the researchers concluded that humans must have brought dogs into the Americas somewhere around 15,000 years ago.
“Dogs are not going to go to the new world without people,” Meltzer tells the New York Times.
Further exploring the dogs’ genetic evidence, the team found all dogs with the genetic signature A2b descended from the same Siberian canines roughly 23,000 years ago, Science reports.
Looking back at human’s ancestral timeline and genetic evidence, the researchers found that ancient Northern Siberians intermingled with ancestral Native Americans before crossing the land bridge into the Americas. These meetings could have resulted in the two groups of people trading pups.
“People are exchanging information, they’re exchanging mates, they’re maybe exchanging their wolf pups,” Meltzer tells the New York Times.
While there is strong evidence that the initial domestication event occurred 23,000 years ago, the study relied only on mitochondrial DNA and could be missing the complete picture of domestication events, explains Pontus Skoglund, an ancient canine DNA expert from Crick Institute in London who was not involved in the study, to the New York Times. Likewise, Peter Savolainen, a geneticist at the Royal Institute of Technology, tells Science that the A2b signature has been found in other places in the world and is not unique to dogs in the Americas as the researchers suggested.
Still, the study reveals how the relationship between humans and dogs may have begun and how it may have dispersed across the globe. Perri and her team plan on looking at older dog fossils to gather more evidence.
"We have long known that the first Americans must have possessed well-honed hunting skills, the geological know-how to find stone and other necessary materials and been ready for new challenges," Meltzer tells Peter Dockrill for Science Alert. "The dogs that accompanied them as they entered this completely new world may have been as much a part of their cultural repertoire as the stone tools they carried."