Remarkable evidence has been uncovered of horse butchery in North America that dates back 24,000 years. The groundbreaking study pushes the timing of the first entry of humans into North America across the Bering Strait back by 10,000 years.
A horse mandible from the Yukon showing the marks of a stone tool apparently used to remove the tongue was dated at 19,650 years radiocarbon years – the equivalent to between 23,000 and 24,000 calendar years ago.
The findings of the study have been published in the open-access peer-reviewed journal PLOS ONE, following work by University of Montreal anthropology professor Ariane Burke and her doctoral student Lauriane Bourgeon, as well as the efforts of Dr Thomas Higham, who is deputy director of Oxford University’s Radiocarbon Accelerator Unit.
The earliest settlement date of North America was, until now, estimated at 14,000 years ago, based on the earliest dated archaeological sites. It is now estimated at 24,000 years ago, at the height of the last ice age or Last Glacial Maximum.
The researchers’ findings arise from painstaking analysis of artifacts removed from the Bluefish Caves, on the banks of the Bluefish River in northern Yukon, not far from the Alaska border.
The site was excavated by archaeologist Jacques Cinq-Mars over a 10-year period from 1977. Cinq-Mars, following radiocarbon dating of animal bones, controversially suggested that human settlement in the area dated back as far as 30,000 years ago.
Although the caves yielded a massive haul of animal bones from the likes of horses, mammoth, bison and caribou, there was no evidence that this accumulation arose from human activity.
Bourgeon, in her research, examined about 36,000 bone fragments that had been taken from the caves and preserved at the Canadian Museum of History in Gatineau. The work took her two years to complete.
Certain bone pieces were taken to the University of Montreal’s Ecomorphology and Paleoanthropology Laboratory, where further work revealed undeniable traces of human activity in 15 bones. About 20 other fragments also showed probable traces of the same type of activity.
Burke says a series of straight, v-shaped lines on bone surfaces were made by stone tools used to skin animals.
“These are indisputable cut-marks created by humans,” she says.
Bourgeon organized further radiocarbon dating of the specimens.
The oldest fragment, a horse jaw showing marks from a stone tool, was radiocarbon-dated at 19,650 radiocarbon years before present, which is equivalent to between 23,000 and 24,000 calendar years ago. The jawbone bears tool marks from efforts to remove the tongue.
“Our discovery confirms previous analyses and demonstrates that this is the earliest known site of human settlement in Canada,” Burke. says. “It shows that Eastern Beringia was inhabited during the last ice age.”
Beringia is a vast region stretching from the Mackenzie River in the Northwest Territories to the Lena River in Russia. According to Burke, studies in population genetics have shown that a group of a few thousand individuals lived in isolation from the rest of the world in Beringia 15,000 to 24,000 years ago.
“Our discovery confirms the ‘Beringian standstill [or genetic isolation] hypothesis’,” she says.
“Genetic isolation would have corresponded to geographical isolation. During the Last Glacial Maximum, Beringia was isolated from the rest of North America by glaciers and steppes too inhospitable for human occupation to the West. It was potentially a place of refuge.”
The Beringians of Bluefish Caves were therefore among the ancestors of people who, at the end of the last Ice Age, colonized the entire continent along the coast to South America.
The different activities on the bones included skinning, dismembering and defleshing.
Cut marks were observed on horse, caribou, wapiti, and possibly dall sheep and bison, as well as a bird shoulder blade.
The researchers said the dating of the oldest bone, the horse jaw, to between 23,000 and 24,000 calendar years ago was consistent with its stratigraphic position in the cave.
The study team said in the journal: “It is highly unlikely that the cut marks observed on the Bluefish Caves faunal material were generated by nonhuman agents or natural processes.”
The marks on the horse mandible and a caribou pelvis were clearly not the result of climatic or soil-related factors or carnivore activity.
“The presence of multiple, straight and parallel marks with internal microstriations observed on both specimens eliminates carnivores as potential agents.”
Previous work on one of the teeth from the horse jaw indicated that the animal was killed in spring/summer, they noted, which suggested a human presence in this particular cave during the warm season.
In another cave, three other bone specimens – a horse humerus, a horse metatarsal and a caribou metacarpal – dated back between 15,000 and 22,000 years ago. The three bones bore v-shaped cut marks on the shaft that could not have resulted from natural processes, they said. They pointed to filleting activity or the stripping of tendons.
In all cases, analysis showed the marks were consistent with those produced by stone tools
They noted that while some prey species became extinct, such as the horse, by around 14,000 years ago, human hunters could have continued to rely on different species such as caribou, bison and wapiti.
Bourgeon L, Burke A, Higham T (2017) Earliest Human Presence in North America Dated to the Last Glacial Maximum: New Radiocarbon Dates from Bluefish Caves, Canada. PLoS ONE 12(1): e0169486. doi:10.1371/journal.pone.0169486