It's well-known that humans and dogs go way back. But how far back? The debate still rages over the timing of that fateful day when humans teamed up with canine companions. And the answer may have just gotten more complicated. A new study suggests that humans in two different parts of the world independently domesticated wolves to produce our lovable modern pooches, Ed Yong reports for The Atlantic.
The study, published in the journal Science, was what the researchers call “a dogged investigation of domestication.” The international team of scientists sequenced DNA of ancient and modern dogs and found that two different wolf populations on two different sides of Eurasia may both be ancestors of the modern canine.
This means that humans in both Asia and Europe may have separately tamed dogs—and could solve longstanding confusion over why modern-day dogs seem to be a mixture of both East and West. Evidence from the dog genome suggests that they were domesticated around 15,000 years ago in Asia. Yet researchers have uncovered even older archaeological evidence of dogs in Europe.
“If I was being bold, I’d put [the strength of our evidence as] a seven out of ten,” Greger Larson, the archaeologist and geneticist who led the team, tells Yong.
The answer seems to be locked inside dogs’ mitochondrial DNA. Since that type of DNA is passed on from mother to child without being altered, it’s a direct link to an animal’s ancestry.
In this case, mitochondrial DNA analysis showed that both Eastern and Western dogs split from one another at dates that are earlier than both the oldest Eastern and Western archaeological evidence of dogs. The only explanation is that dogs were domesticated independently in both the East and West.
At some point, however, Western dogs seem to have dwindled. Domesticated Eastern dogs—who were brought to Europe by migrants—then mated with the remaining Western dogs. This intermingling created an East-West hybrid that replaced the pure Western domesticated pooches. Meanwhile, the original Eastern dogs continued to breed in Asia.
Larson uses the word “bold” for a reason—there’s still no evidence of a unique Western wolf ancestor. As Tim Radford explains it in The Guardian, this intermingling of East and West scrambled the genetic evidence and without a surviving pure-bred Western-domesticated pup, it is difficult to prove this idea to be true.
There’s still work to do: In a release, the team says that they plan to put their theory to the test by analyzing thousands of ancient dogs and wolves. If their theory holds, it would rewrite the story of how our beloved pets came to be.