Ancient dog bones Evidence of the route humans took to North America

A 10,000-year-old fragment of dog bone found along the Alaskan coast may be the oldest evidence of domestic dogs in North America and potential evidence of a coastal route taken by the original inhabitants of North America from Eurasia.

Evidence continues to mount for the coastal migration theory, which proposes that Eurasian migrants, instead of traveling through an interior corridor between two molten ice caps, embraced the Siberian, Beringian and Alaskan coasts. . These settlers continued their way along the Pacific coast, eventually reaching the southern limit of the enormous Cordillera ice cap, according to this theory.

The coastal migration theory, also known as the kelp route hypothesis, is supported by geological and archaeological evidence, including 29 human footprints found on the shore of Calvert Island in British Columbia. We now have more evidence to support this theory, but it comes from an unexpected source: a domestic dog.

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

The fact that Alaska was home to dogs around this time is not a huge surprise. 2019 research presented evidence of three prehistoric dogs found buried in what is now Illinois, which were dated between 9,630 and 10,190, the latter figure suggesting a date slightly older than the date presented for the femur in the new document. I asked Lindqvist about this apparent discrepancy.

“When you compare the median radiocarbon dates of the Illinois dogs and our dog, the Alaskan dog is a bit older,” she says. “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 tell they’re at least close to the same age, maybe with the Alaskan dog a few hundred years older. “

The Illinois dogs are important because they suggest that the first settlers from North America brought their dogs with them from Eurasia. Previous genetics search fact in this area came to a similar conclusion, showing that dogs arrived in the Americas about 10,000 years ago.

Lindqvist and his colleagues inadvertently fell on the femur while sequencing DNA from a jumble of animal bones collected from caves in Southeast Alaska. This research aims to determine how climate change during the last ice age affected various species, including their mobility.

“One of the projects I’m working on is black and brown bears and we initially thought the bone was from a bear, but later found out it was a dog, and we had to follow up on this discovery, ”Lindqvist explained in an email.

The canine femur fragment, designated PP-00128, was found on the southeastern mainland of Alaska, just east of Wrangell Island, in a location known as Lawyer’s Cave. Lindqvist, along with his co-author Timothy Heaton, professor of earth sciences at the University of South Dakota, conducted a number of excavations in the late 1990s and early 2000s, culminating in the discovery of this bone and many others from this same cave.

The team was able to extract a complete mitochondrial genome from the fragment, which they compared to modern dog breeds, historic arctic dogs, and pre-contact American dogs (i.e. dogs that lived in the Americas before the arrival of Europeans). Mitochondrial DNA comes exclusively from the maternal side, so it’s incomplete (compared to nuclear DNA), but scientists were able to trace the genome to a line that diverged from Siberian dogs around 16,700 years ago. .

This is important, because this “timing roughly coincides with the suggested minimum date for the opening of the North Pacific Coastal Route along the Cordillera Ice Cap and genetic evidence for the initial settlement of the Americas,” as the authors wrote in the study.

Indeed, the fragment PP-00128 presents another clue in favor of the hypothesis of coastal migration. The coastal edge of the ice cap began to melt about 17,000 years ago, while the interior corridor only opened about 13,000 years ago.

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

Prior to the new study, “the oldest American dog remains were found at mid-continent sites, with no indication of how they got there,” she said, but this latest finding “confirms that our coastal dog is a descendant of dogs that participated in this first migration along the Pacific Northwest coast. “

It’s possible, of course, that this was a rogue dog that somehow made it to North America without the humans. It’s not as weird 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 said, Lindqvist believes her Alaskan dog likely lived with humans.

“Other excavated remains from this same cave include human bones and artifacts, but they are all younger,” she said. “They suggest, however, 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 area when this ancient dog lived. But no, we don’t have direct evidence that this dog lived with humans. We do know, however, that this dog was a servant and not a wolf, and if I were a dog, I would likely stay near humans for food.

Indeed, an analysis of the carbon isotopes of the fragment of femur suggests that this dog was fed by humans, because it ate fish (possibly salmon) and the meat of whales and seals. This contrasts sharply with other ancient dogs living in the center of the continent, who exhibited a “much more earthly diet,” Lindqvist said.

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

“We already know from several sites that soutAlaska was occupied 12,600 years ago, which is 2,400 years earlier than the dog, ”he explained via email. “So it is quite uninformative about the routes of the early Native Americans about 4,000 to 5,000 years earlier.”

This huge time lag, he said, is “equivalent to the emergence of the first Near Eastern states – ancient Egypt and Mesopotamia – and today.”

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

That humans traveled along the Pacific coast from Eurasia to North America seems highly likely, and the new research fits perfectly into this increasingly popular narrative. But that doesn’t mean that alternative routes to the continent have been overlooked. As Potter points out, there was probably more than one route in North America, because 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.