On the trail of the first dogs to put their paws in the Americas

A boxer dog peeps out from its kennel. The breed was developed in Germany in the 19th century and imported to America after the first world war. Photograph: Matt Cardy/Getty

Humans began migrating to the Americas roughly 15,000 to 20,000 years ago. But domesticated canines likely didnt show up on American continents until 10,000 years ago, long after humans first arrived, according to a new analysis of ancient dog DNA by University of Illinois researchers. Their findings were published in the Journal of Human Evolution.

We were interested in seeing if we could see when dogs arrived in the Americas, said study author Kelsey Witt. Its assumed they came with humans, but no one has actually looked at it.

Dogs very likely were domesticated in Asia and then brought over to the Americas, Witt said. What we know about ancient dogs so far is that by the time Europeans arrived, they were pretty widely spread across the Americas. They were used to haul supplies, used as guards, had religious significance for some, used as a food source.

For this study, researchers analysed the remains of 84 dogs, including 34 from a single burial site in Illinois that dates back about 1,000 to 1,400 years. They specifically examined mitochondrial DNA, which is inherited maternally and allows a direct look back at a lineage. Previous studies only had access to about 40 such dog remains.

The genetic diversity of the dogs was only about 10,000 years old. And the newly studied dogs were closely related, which suggests that humans may have been breeding the animals, Witt said.

However, Witt said its possible their results were skewed because they were working with very old and disintegrated DNA. You cant always sequence as much as you might like, she said. Her next project involves working with a much longer stretch of DNA to see if she can replicate similar results.

The dogs arriving in the Americas were genetically similar to European wolves, and a prevalent theory is that some went on to breed with American wolves, Witt said.

Given that dogs have been an integral part of human life for so long, learning about their ancient history also means we are learning about our own. Witt said sequencing the DNA of ancient humans can be extremely challenging, especially when people dont want their ancestors remains destroyed or disturbed. Dogs can serve as a good proxy. Also, although humans in the American midwest were burying dogs about 1,000 years ago, they werent burying people.

The late arrival of dogs suggests that there may have been a second, major migration of humans as well. And once dogs arrived, they quickly spread, which tells us more about human movement.

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On the trail of the first dogs to put their paws in the Americas