The skeletal remains of the Stillwell II dog.
Image: Del Baston/Center for American Archaeology

The skeletal remains of three ancient dogs found buried in Illinois now represent the earliest evidence for the presence of domesticated dogs in the Americas. It’s also the oldest known intentional burial of individual canines in the global archaeological record.

Domesticated dogs have been in North America for at least 10,000 years, according to new research published in American Antiquity. This finding is based on the re-analysis of three dog skeletons found in Illinois in the 1960s and 1970s by the self-taught American archaeologist Gregory Perino. The remains, which had been stored at the Illinois State Museum, hadn’t been properly dated using modern techniques, leading to the new analysis, led by Angela Perri from Durham University in the United Kingdom.

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Two of the dogs were found at the Koster site in the Lower Illinois River Valley and one was found at the nearby Stillwell II site. Direct carbon dating of the Koster and Stillwell remains yielded a date between 9,630 and 10,190 years ago, which is around 1,000 years earlier than conventional estimates; previously, the oldest confirmed remains of a North American dog came from a 9,300-year-old site in Texas. Together, the Koster and Stillwell specimens represent the “earliest confirmed archaeological dog record in the Americas,” and the “oldest individually-buried dogs known in the worldwide archaeological record,” the authors wrote in the study.

The new dates are consistent with genetic evidence published last year, suggesting domesticated dogs were in the Americas around 10,000 years ago.

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That sounds like a long time ago—and it is—but the first people arrived in North America around 15,000 years ago, if not earlier, as the last Ice Age was ending, and they did so by hugging the coastline or traveling through Beringia via a gap in the massive ice sheets, or a combination of the two. The first domesticated dogs appeared in Eurasia no later than 16,000 years ago, and possibly as long ago as 40,000 years ago. It’s a good bet, therefore, that America’s first human migrants brought their canine companions along with them, though archaeological evidence to that effect is sorely lacking.

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That they would do so makes a lot of sense.

“Dogs may have assisted migrating groups by transporting goods and people, working as hunting aids, serving as bed-warmers, acting as alarms, warding off predators, and as a food and fur source,” wrote the authors in the new study.

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But as the new research shows, there’s about a 5,000-year archaeological gap between the presence of humans in the Americas and the presence of domesticated dogs. This observation suggests one of two possibilities: Either dogs traveled to North America alongside humans and the archaeological evidence is lacking, or dogs arrived later during subsequent human migrations. Given the evidence (or lack thereof), both scenarios are plausible. A third scenario, that the earliest dogs in North America were domesticated from indigenous wolves, was effectively disproven by a genetic analysis conducted last year, showing that the genomes of the earliest American dogs were closely related to Arctic breeds, such as Siberian Huskies.

As already noted, the dogs found at Koster and Stillwell II were intentionally buried. Last year, archaeologists in Germany uncovered a 14,200-year-old dog burial, but because the dog was buried alongside humans, it’s not considered an individual burial. The Koster dogs were found buried in individual, shallow, well-demarcated pits, while the lone Stillwell dog was found buried beneath the floor of a living area with its front legs tucked under its body. These intentional burials, it seems to me, may have represented a new human behavior, leading to the enhanced preservation of dog remains, and a possible explanation as to why earlier dogs are so scarce in the archaeological record.

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That said, ancient dog remains have been uncovered across Beringia and southern Siberia dating back to between 17,200 and 12,800 years ago, and a number of tantalizing candidates have been found in North America, but the dating of those remains has proved inconclusive and controversial. The new study, on the other hand, is the first to use modern chronological and physical evaluation techniques to conclusively date and identify ancient canine remains in the Americas.

Leiden University PhD candidate and veterinarian Luc Janssens, who was involved in the discovery of the 14,200-year-old dog grave in Germany, was excited about the new research, telling Gizmodo it was “excellent.”

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An updated skeletal analysis of the three canine remains was conducted by Perri and her colleagues at Illinois State Museum’s Research and Collections Center. Because no evidence of butchering or skinning was found on the bones, the researchers are confident that the dogs were treated as pets and not food. Isotope analysis showed the dogs lived on a steady diet of river-sourced fish.

Prior to this study, a different team of researchers was able to extract DNA samples from the Koster dogs, but not the Stillwell sample. Genetic analysis showed that the Koster dogs likely came from Siberian stock. If there’s a weakness to this study, it’s in this area.

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“The study has no genetic data and is just a dating project,” Bridgett vonHoldt, a geneticist and expert on early dogs at Princeton’s department of Molecular Biology who wasn’t affiliated with the new research, told Gizmodo. “It simply means that dog remains are older than thought and may have arrived here earlier than we thought.”

To be fair, the researchers did perform an updated skeletal analysis of the dogs. In terms of size, the Stillwell dog, likely a female, featured a mass and build similar to a small modern English Setter, standing around 20 inches tall at the shoulders and weighing somewhere between 37 and 70 pounds. The dogs from the Koster site were slightly smaller and shorter.

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Mandibles of the Stillwell specimen, showing advanced tooth wear.
Image: A. Perri et al., 2019

Interestingly, the Stillwell dog showed signs of periodontal disease and severe tooth wear; its first and and second molars were extremely worn down, and its right lower canine was practically blunt. This wear-and-tear was likely the result of a lifetime of chewing on bones, the researchers said.

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“Without regular dental care, modern domestic dogs commonly develop similar oral pathology, and from the perspective of modern veterinary medicine, the Stilwell II dog would have been very uncomfortable,” the authors wrote.

According to Perri and her colleagues, early American dogs “likely played key cultural and ecological roles” in the lives of humans, and their “intentional burials suggests they were an important part of human domesticity” in the Americas by the late Paleolithic period. But the arrival of dogs to the Americas was not without environmental impact. These canines were very likely among the first domesticated species to reach America. This development likely impacted “populations of small mammals through predation, other species of [dogs] through hybridization, and other carnivores through transmission of diseases or competition,” the authors wrote, adding that these dogs “may have also contributed to important adaptations in hunting and mobility during the peopling of the Americas and into the Pleistocene-Holocene transition.”

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This study, while both interesting and revealing, poses more questions than it answers. Looking ahead, scientists should continue the search for more dog burials, and perform more genetic analyses to confirm dates and places of origin, and to see if different populations of American dogs were interbreeding amongst themselves, and possibly with indigenous species, namely wolves.

The more we learn about this important phase of history, the better our understanding of how the Americas were settled—and how our canine companions played a part.

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[American Antiquity]