LGM occupation of Eastern Beringia at Bluefish Caves

Earliest Human Presence in North America Dated to the Last Glacial Maximum: New Radiocarbon Dates from Bluefish Caves, Canada

Lauriane Bourgeon, Ariane Burke, Thomas Higham
PLoS ONE 12(1): e0169486. doi:10.1371/journal.pone.0169486

The timing of the first entry of humans into North America is still hotly debated within the scientific community. Excavations conducted at Bluefish Caves (Yukon Territory) from 1977 to 1987 yielded a series of radiocarbon dates that led archaeologists to propose that the initial dispersal of human groups into Eastern Beringia (Alaska and the Yukon Territory) occurred during the Last Glacial Maximum (LGM). This hypothesis proved highly controversial in the absence of other sites of similar age and concerns about the stratigraphy and anthropogenic signature of the bone assemblages that yielded the dates. The weight of the available archaeological evidence suggests that the first peopling of North America occurred ca. 14,000 cal BP (calibrated years Before Present), i.e., well after the LGM. Here, we report new AMS radiocarbon dates obtained on cut-marked bone samples identified during a comprehensive taphonomic analysis of the Bluefish Caves fauna. Our results demonstrate that humans occupied the site as early as 24,000 cal BP (19,650 ± 130 14C BP). In addition to proving that Bluefish Caves is the oldest known archaeological site in North America, the results offer archaeological support for the “Beringian standstill hypothesis”, which proposes that a genetically isolated human population persisted in Beringia during the LGM and dispersed from there to North and South America during the post-LGM period.

The cut-marked horse (Equus lambei) mandible dated to 24.033–23.314 cal kaBP. The bone surface is a bit weathered and altered by root etching but the cut marks are well preserved; they are located on the medial side, under the third and second molars, and are associated with the removal of the tongue using a stone tool.

Glad to hear the dam crack.

Thought experiment: Suppose the butchers were ancestral “First Americans” somewhere upstream of Anzick-1 (our only Late Pleistocene American genome to date) and the Holocene lineages that phylogenetically bracket him. If so, these finds could also have important implications for Eurasian peopling. Given the prevailing model of “First Americans” as “Ancient North Eurasian” (ANE) + “East Asian” without significant heterogeneity in the proportions, we would likely have to reject visions of “East Asian” ancestry as a post-LGM arrival to the far north — instead finding some stream of it already in place in eastern Siberia or the northern Russian Far East >24 kaBP. (There are exotic alternatives: for instance, first settling Beringia with unadmixed ANE people who only later — though still earlier than the deepest internal First American splits — meet and homogenize with East Asian migrants.) The new dates make Bluefish Caves contemporaneous with the Mal’ta child, our canonical ANE sample.

Administrative note: Have been preoccupied with my final semester of required coursework and upcoming qualifying exams but will be blogging more regularly come February. I look forward to defrosting many thoughts I’ve shelved in cold storage.