The Bluefish Basin discovery
At the base of a limestone ridge, 54 kilometers from the Vuntut Gwitchin village of Old Crow, lie three small caves. These are the Bluefish Caves, a site that has reshaped the timeline of human arrival in North America. Between 1977 and 1987, archaeologist Jacques Cinq-Mars led excavations here, unearthing a collection of around 36,000 animal bone fragments. The collection included a variety of Ice Age fauna, including the bones of woolly mammoth (Mammuthus primigenius), steppe bison (Bison priscus), caribou (Rangifer tarandus), and a now-extinct species of Yukon horse (Equus lambei).
Cinq-Mars's initial analysis suggested some bones showed signs of human modification and dated them to a period much earlier than the established 13,000-year-old "Clovis First" model for human presence in the Americas. His hypothesis was met with widespread skepticism from the scientific community for decades. The caves, with a volume from only 10 to 30 cubic meters, were seen by many as places where animal predators dragged carcasses, and any bone breakage was attributed to natural processes like rockfall.
A 10,000-year problem
Decades after the initial excavations, a new analysis vindicated Cinq-Mars's original claims. Researchers Lauriane Bourgeon and Ariane Burke from the Université de Montréal re-examined the bone collection. Using high-powered microscopy, they identified 15 bone fragments with clear evidence of human activity. The surfaces of these bones displayed distinctive, straight, V-shaped lines consistent with cut marks made by stone tools used to skin and butcher animal carcasses.
The team selected several of these marked bones for modern Accelerator Mass Spectrometry (AMS) radiocarbon dating. The results were clear. The oldest sample, a horse mandible with cut marks linked to the removal of the tongue, was dated to as early as 24,000 calibrated years Before Present (cal BP). This date places humans in North America 10,000 years earlier than the Clovis culture and squarely within the Last Glacial Maximum.
This evidence supports the "Beringian Standstill Hypothesis." This model suggests a population of humans lived genetically isolated in Beringia—the landmass that connected Asia and North America—during the ice age. The 24,000-year-old date at Bluefish Caves shows people were living in Eastern Beringia when their path south was blocked by massive continental ice sheets, forcing a long pause before they populated the rest of the Americas.