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There's Human History Hiding in Ancient Dog Remains

Anthropologists say you can find cultural, dietary, and even genetic information about humans by studying their dogs.
Artwork discovered at Pompeii. Image: ​Marisa Panetta/Wikimedia Commons

​Before humans domesticated the cow, the sheep, or even the chicken, they domesticated dogs. Our companion dating way back to our mammoth slaying days, the fates of dog and human have been intertwined so closely and for so long, researchers now believe that if they have a gap when researching ancient human populations, looking at the dogs from the same time and place could help fill them in. If you can't reach the source, I guess you go to the best friend, and there you'll find cultural, dietary, even genetic information.

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Kelsey Witt, a graduate student at the Malhi lab of molecular anthropology at the University of Illinois, Urbana-Champaign, is the lead author ofa study just published in the Journal of Human Evolution. Despite the journal's name, the study is the largest yet that looks at ancient dogs in the Americas. She told me that the genetic information indicates that domestication happened before humans migrated from Eurasia.

"Most dog remains that have been sequenced are more closely related to Eurasian wolves than American wolves, suggesting that dogs were already domesticated in Europe when they arrived in the Americas," Witt told me.

She noted that some dogs, especially some found in sites in Canada, show some genes that are closer to American wolves, but its unclear if dogs started interbreeding with wolves when they arrived, or if there was a second domestication event in America. At any rate, "human migration to the Americas likely occurred around 15,000-20,000 years ago, so that's the timing we're working with," Witt said.

As hunting companions, beasts of burden, and even occasionally as a food source, dogs have accompanied humans to every continent. But Witt's research, which looked at genetic information from 84 different dogs spread across over a dozen sites in North and South America, indicates that the first humans to migrate to the Americas did so dogless. Just like in the movie Homeward Bound, though, the dogs showed up later, which again tells us something about human migration.

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"Our research suggests that dogs may have arrived as recently as 10,000 years ago, thousands of years after the first humans arrived," Witt said. "If dogs migrated to the Americas around 10,000 years ago, they undoubtedly migrated with humans. So, if dogs migrated to the Americas later, we are also suggesting that there was a secondary migration of humans at the same time. Additional migration events following the initial migration has been suggested in the literature, so this idea is not unheard of."

Beyond the changing time frames and geography, the ancient human and dog team-up changed each species.

"Dogs and humans probably migrated together, and so as they moved around, their genomes probably changed in similar ways," Witt said, citing how both humans and dogs have evolved to eat more grains, which makes sense because dog and human diets are so intertwined. Diets that are rich in marine life, or meat or plants leave evidence that shows up in isotope analysis of dog remains, which again points back to their human companions.

"We can compare genomes between populations to determine migration routes or look at interactions between populations," Witt said. "When human remains are unavailable for study (for ethical reasons or otherwise), DNA from dog remains might be a good way to 'fill in gaps' in knowledge."

But before the bones of ancient dogs are even out of the ground, they can tell researchers quite a bit.

"We can also use dogs to inform about human populations culturally. The dog burials themselves can say a lot about human culture and how a particular population valued or treated their dogs, whether they were buried deliberately or thrown into a trash pile," Witt said. "We can also use skeletal clues to get an idea of how they were used, whether it was for food or as pack animals or as hunters of game. The presence of dog (or any animal) remains at an archaeological site can be more informative than just the presence of human burials."

The research tells us a lot about both ancient dogs and ancient humans, which is unsurprising, since it's hard to study one with studying the other. There's an old adage that eventually people start to look like their pets, but it appears that this convergence has been in the making for a long, long time.