A 10,000-year-old dog bone fragment found along the Alaska coast could be the oldest evidence of North American domestic dogs and potential evidence of a coastal route taken by the first humans to cross North America. from Eurasia.
Evidence continues to grow for the theory of coastal migration, which proposes that Eurasian migrants, instead of traveling through an inner corridor between two layers of melting ice, embraced the Siberian, Beringian and Alaska coasts. These settlers continued their journey along the Pacific coast, eventually reaching the southernmost limit of the massive ice sheet in the Cordilleran, according to this theory.
The theory of coastal migration, also known as the Kelp Highway Hypothesis, is supported by geological and archaeological evidence, including 29 human traces found on the shores of Calvert Island in British Columbia. We now have other evidence to support this theory, but it comes from an unexpected source: a domesticated dog.
This dog died about 10,150 years ago in what is now Alaska, right at the end of the last ice age. The lone fossil – a piece of femur – is now the oldest confirmed remains of a domesticated dog in America, according to new research, led by evolutionary biologist Charlotte Lindqvist of the University of Buffalo. The paper describing this discovery was published Tuesday in the Proceedings of the Royal Society B.
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The fact that Alaska was home to dogs during this period is not a huge surprise. Research from 2019 presented evidence of three prehistoric dogs found buried in what is now Illinois, which were dated between 9,630 and 10,190 years ago, the latest figure suggesting a date slightly older than the date presented for the femur in the new paper. I asked Lindqvist about this apparent discrepancy.
“When you compare the average radiocarbon data of Illinois dogs and our dog, the Alaska dog is a little older,” she said. “But it depends on what you’re comparing, and with the error bars and the uncertainty – and the radiocarbon dating done by different labs – you can say that they’re at least about the same age, possibly the dog in Alaska being a few hundred years older. age. ”
Dogs in Illinois are significant because they suggest that the first settlers in North America brought their dogs with them from Eurasia. Previous genetics research conducted in this area came to a similar conclusion, showing that dogs arrived in America about 10,000 years ago.
Lindqvist and her colleagues accidentally hit their femurs while sequencing DNA from a mixture of animal bones excavated in caves in southeast Alaska. This research is done to determine how climate change in the last glacial era has affected various species, including their mobility.
“One of the projects I’m working on involves black and brown bears and I initially thought the bone came from a bear, but later I found out it was a dog and we had to follow that finding,” Lindqvist explained in an e-mail. mail.
The fragment of the canine femur, designated PP-00128, was found on southeastern Alaska, east of Wrangell Island, in a location known as the Lawyer’s Cave. Lindqvist and her co-author Timothy Heaton, a professor of earth sciences at the University of South Dakota, conducted a series of excavations in the late 1990s and early 2000s, resulting in the discovery of this bone and many others from the same cave.
The team was able to obtain a complete mitochondrial genome from the fragment, which they compared to modern breeds of dogs, historic Arctic dogs and American dogs before contact (ie dogs that lived in America before the arrival of Europeans). Mitochondrial DNA comes exclusively from the mother, so it is incomplete (compared to nuclear DNA), but scientists have been able to trace the genome back to a offspring that diverged from Siberian dogs about 16,700 years ago.
This is significant because this “time roughly coincides with the suggested minimum date for the opening of the North Pacific coastline along the Cordillerian ice sheet and genetic evidence for the original American population,” as the study authors wrote.
Indeed, fragment PP-00128 shows another indication in favor of the coastal migration hypothesis. The shoreline of the ice sheet it began to melt about 17,000 years ago, while the inner corridor it has not opened until about 13,000 years ago.
“Previous genetic estimates of the division between pre-European American dogs and their Siberian ancestors were younger than estimates at the time the ancestral American human population diverged from their Siberian ancestors, suggesting that dogs reached later human migrations to America, maybe even along the inner corridor, ”Lindqvist explained.
Prior to the new study, “the oldest remains of American dogs were found on the sites of the Middle Continent, without suggesting how they got there,” she said, but this latest finding “claims that our coastal dog is a descendants of dogs that participated in this initial migration along the northwest Pacific coast. ”
There is, of course, the possibility that this is a rogue dog that has somehow made its way to North America without humans. It’s not as bizarre as it sounds; dogs were domesticated from wolves between 14,000 and 29,000 years ago, in a complex process that involved multiple episodes of crossbreeding between dogs and wild wolves. That being said, Lindqvist believes her dog from Alaska probably lived with humans.
“Other remains excavated in the same cave include human bones and artifacts, but all of them are younger,” she said. “However, they suggest that the cave was actually used by humans. And we know from human remains found in another cave in southeast Alaska that people were in the area when this ancient dog lived. But no, we have no direct evidence that this dog lived with humans. We know, however, that this dog was a domestic and not a wolf, and if I were a dog, I would probably sit around people to eat. ”
Indeed, an analysis of the carbon isotope of the femoral fragment suggests that this dog was fed by humans because it ate fish (possibly salmon) and meat from whales and seals. This is in stark contrast to other ancient dogs living in the middle of the continent, which had a “much more terrestrial diet,” Lindqvist said.
Ben Potter, an archaeologist at the Arctic Studies Center at Liaocheng University in China, had some concerns about new study.
“We already know through several supportive sitesheast Alaska was occupied 12,600 years ago, which is 2,400 years earlier than the dog, ”he explained by e-mail. “So it’s completely uninformative about the routes of the first Native Americans about 4,000 to 5,000 years earlier.”
This huge time lag, he said, is “equivalent to the emergence of the first states in the Middle East – ancient Egypt and Mesopotamia – even today.”
To which Potter added: “Our review of the data indicates that the inner route of the ice-free corridor was available at least 14,900 years ago. ‘
That people have traveled along the Pacific coast from Eurasia to North America seems highly likely, and the new research fits nicely with this increasingly popular narrative. But this does not mean that alternative routes to the mainland have been neglected. As Potter points out, it probably existed more than one route in North America, because an inner corridor probably opened about 12,600 to 14,900 years ago.
This post has been updated to include comments received by Ben Potter.