How Dogs and Humans Evolved and Migrated in Tandem

Where many ancient people went, their dogs followed. Still, other human ancestors opted to adopt locally when they arrived at their new homestead, a new study in the journal Science suggests. This new analysis of both canine and human DNA reveals new details of our evolving relationship with our furry friends.

"Dogs are really unique in being this quite strange thing if you think about it. When all people were still hunter gatherers, they [domesticated] what is really a wild carnivore," Pontus Skoglund, study author and geneticist at the Francis Crick Institute in London, tells Paul Rincon for BBC. "The question of why did people do that? How did that come about? That's what we're ultimately interested in."

To piece together this timeline, an international team of researchers examined more than 2,000 remains of ancient dogs, reports David Grimm for Science magazine. Of those specimens, they sequenced the DNA of 27 dogs from across Europe, the Near East and Siberia that lived between 800 and 11,000 years ago.

Then, they compared those samples to ancient human DNA from similar places and time periods as the dogs to trace their evolutionary lineages.

"It’s like you have an ancient text in two different languages, and you’re looking to see how both languages have changed over time," Skoglund tells Science.

Sometimes, humans and dogs shared ancestral origins. For example, dogs and humans that lived around 5,000 years ago in Sweden both originated in the Near East. Perhaps, as agriculture expanded westward, some canine companions tagged along.

In other cases, human migrants adopted local dogs that were more acclimated to the region. Farmers in Germany living 7,000 years ago also originated in the Near East, but their dogs came from European and Siberian lineages.

"We find that when we compare the history of dogs to the history of humans, to a quite large degree they mirror each other, suggesting that in many cases, the history of dogs has been shaped by humans," Anders Bergstrom, the study’s lead author and geneticist at the Francis Crick Institute, tells CNN’s Amy Woodyatt. "[In] some cases, dogs display different history, suggesting there were more complex factors at play: Perhaps sometimes people moved without bringing their dogs, or perhaps sometimes dogs were traded between human groups."

Their analysis also revealed that by the end of the last ice age—around 11,000 years ago—at least five distinct lineages of dogs existed in New Guinea, the Americas, northern Europe, the Near East and Siberia. To achieve this genetic diversity, dogs had to have been domesticated much earlier, supporting the archaeological evidence that the origin of canine domestication goes back to 15,000 years ago, reports Science.

The team also mapped how ancient DNA can be traced in today's pups. For example, Siberian huskies carry DNA from the ancient lineage originating in Siberia, and chihuahuas have genetic roots in Mexico.

"[If] I walk through Wimbledon Common, I am pretty likely to run across dogs that all have a little bit [of a] different history, tracing back as far as 11,000 years ago to different corners of the world," Skoglund tells Nicola Davis for The Guardian.

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Rasha Aridi is a science journalist based in Richmond, Virginia. She has written for Science magazine and Science News for Students. You can find her portfolio at rashaaridi.com.