Sometime toward the end of the last ice age, a gray wolf gingerly approached a human encampment. Those first tentative steps set his species on the path to a dramatic transformation: By at least 15,000 years ago, those wolves had become dogs, and neither they nor their human companions would ever be the same. But just how this relationship evolved over the ensuing millennia has been a mystery. Now, in the most comprehensive comparison yet of ancient dog and human DNA, scientists are starting to fill in some of the blanks, revealing where dogs and humans traveled together—and where they may have parted ways.
“It’s a really cool study,” says Wolfgang Haak, an archaeogenetic at the Max Planck Institute for the Science of Human History. “We’re finally starting to see how the dog story and the human story match up.”
Dogs are one of the biggest enigmas of domestication. Despite decades of study, scientists still have not figured out when or where they arose, much less how or why it happened. A 2016 study concluded that dogs may have been domesticated twice, once in Asia and once in Europe or the Near East, but critics said there was not enough evidence to be sure. A few years later, researchers reported signs of dogs in the Americas as early as 10,000 years ago, yet those canines appear to have vanished without a genetic trace. Other studies have found evidence of ancient dogs in Siberia and elsewhere, but scientists do not know how they got there or how they’re related.