Ancient dog bone, evidence of the route humans took to North America


The canine bone fragment, found in southeast Alaska.

The canine bone fragment, found in southeast Alaska.
Picture: Douglas Levere / University at Buffalo

A 10,000-year-old dog bone fragment found along the Alaskan coast could be the oldest evidence of domesticated dogs in North America and potential evidence for a coastal route taken by the first people to cross into North America. from Eurasia.

Evidence continues to mount for the Coastal Migration Theory, which proposes that Eurasian migrants, rather than traveling down an inland corridor between two melting ice sheets, hugged the coasts of Siberia, Beringia and Alaska. These settlers continued their way along the Pacific coast, finally reaching the southernmost limit of the enormous Andean ice sheet, according to this theory.

The coastal migration theory, also known as the Kelp Highway hypothesis, is supported by geological Y archaeological evidence, including 29 human footprints found off the coast of Calvert Island in British Columbia. We now have more evidence to support this theory, but it comes from an unexpected source: a domesticated dog.

A map showing where the bone fragment was found.

A map showing where the bone fragment was found.
Picture: Bob Wilder / University at Buffalo

This dog died approximately 10,150 years ago in what is now Alaska during the end of the last Ice Age. The single fossil, a piece of femur, is now the oldest confirmed remnant of a domesticated dog in the Americas, according to new research, led by evolutionary biologist Charlotte Lindqvist of the University at Buffalo. The article describing this discovery was published Tuesday in the Proceedings of the Royal Society B.

The fact that Alaska was hosting dogs around this time is not much of a surprise. 2019 research presented evidence Of three prehistoric dogs found buried in what is now Illinois, dating to between 9,630 and 10,190 years ago, the latest figure suggests a date slightly older than the date presented for the femur in the new article. I asked Lindqvist about this apparent discrepancy.

“When you compare the radiocarbon mean dates of the Illinois dogs and our dog, the Alaskan dog is a bit older,” he 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, it can be argued that they are at least the same age, possibly with an Alaskan dog of about two hundred. years older “.

Illinois dogs are important, because they suggest that early North American settlers brought their dogs from Eurasia. Previous genetics research done in this area came to a similar conclusion, showing that dogs came to the Americas approximately 10,000 years ago.

Lindqvist and his colleagues inadvertently stumbled on the femur while sequencing DNA from a jumble of animal bones excavated from caves in Southeast Alaska. This research is being conducted to determine how climate changes during the last Ice Age affected various species, including their mobility.

“One of the projects I work on involves black and brown bears and we initially thought the bone came from a bear, but then we found out it was a dog, and we had to follow up on this finding,” Lindqvist explained in an email. .

The canine femur fragment, designated PP-00128, was found in southeast mainland Alaska, east of Wrangell Island, at a location known as Lawyer’s Cave. Lindqvist, with his 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 this same cave.

University of Buffalo doctoral student Flavio Augusto da Silva Coelho holds the fragment.

University of Buffalo doctoral student Flavio Augusto da Silva Coelho holds the fragment.
Picture: Douglas Levere / University at Buffalo

The team were able to derive a complete mitochondrial genome from the fragment, which they compared to modern dog breeds, historic Arctic dogs, and pre-contact American dogs (that is, dogs that lived in the Americas before the arrival of Europeans). Mitochondrial DNA comes exclusively from the maternal side, so it is incomplete (compared to nuclear DNA), but scientists were able to trace the genome back to a lineage that separated from Siberian dogs about 16,700 years ago.

This is significant, since this “moment roughly coincides with the minimum date suggested for the opening of the North Pacific coastal route along the Cordillera ice sheet and the genetic evidence of the initial settlement of the Americas”, as the authors wrote in the study.

In fact, the PP-00128 fragment presents another clue in favor of the coastal migration hypothesis. The coastal edge of the ice sheet. began to melt about 17,000 years ago, while the inner corridor it wasn’t opened until about 13,000 years ago.

“Previous genetic estimates of the split between pre-European American dogs and their Siberian ancestors were more recent than estimates of when the Native American ancestral human population diverged from their Siberian ancestors, suggesting that the dogs arrived in later migrations from humans to the Americas, perhaps even along the inner corridor, ”Lindqvist explained.

Before the new study, “the oldest American dog remains were found at mid-continent sites, which doesn’t suggest how they got there,” he said, but this latest discovery “supports that our shore dog is a descendant of dogs that participated in this initial study. migration along the Pacific Northwest coast “.

There is a possibility, of course, that it was a rogue dog that somehow made it to North America without humans. That’s not as outlandish as it might sound; Dogs were domesticated from wolves between 14,000 and 29,000 years ago, in a complex process that involved multiple episodes of interbreeding between dogs and wild wolves. That being said, Lindqvist believes that his Alaskan dog likely lived with humans.

“Other remains excavated from this same cave include human bones and artifacts, but they are all younger,” he said. “However, they suggest that the cave was indeed used by humans. And we know from human remains found in another cave in southeast Alaska that humans were in the region at the time this ancient dog lived. But no, we have no direct evidence that this dog lived with humans. However, we do know that this dog was a domesticated and not a wolf, and if I were a dog, I would probably stick with humans for food. “

In fact, a carbon isotope analysis of the femur fragment suggests that this dog was fed by humans, as it ate fish (possibly salmon) and meat from whales and seals. This is in stark contrast to other ancient dogs that lived on the middle continent, which featured a “much more terrestrial diet,” Lindqvist said.

Ben Potter, an archaeologist at the Liaocheng University Center for Arctic Studies in China, had some concerns about the new study.

“We already know through various sites that ariseAlaska was occupied for 12,600 years ago, which is 2,400 years before the dog, ”he explained by email. “Therefore, it is not informative about the routes of the first Native Americans between 4,000 and 5,000 years earlier.”

This immense span of time, he said, is “equivalent to the rise of the first states in the Near East, ancient Egypt and Mesopotamia, and today.”

To which Potter added: “Our review of the data indicates that the ice-free interior corridor route was available at least 14,900 years ago.”

It seems highly likely that humans traveled along the Pacific coast from Eurasia to North America, and the new research fits well with this increasingly popular narrative. But that does not mean that alternative routes to the mainland have been neglected. As Potter points out, it is likely that more than one route in North America, as an interior corridor probably opened about 12,600 to 14,900 years ago.

This post has been updated to include comments received by Ben Potter.

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