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

  • ️Sun Jan 01 2017

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

Lauriane Bourgeon et al. PLoS One. 2017.

Abstract

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.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Cut marks on a horse mandible from Cave II.

The specimen (# J7.8.17) is dated to 19,650 ± 130 14C BP (OxA-33778). 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 [48].

Fig 2
Fig 2. Cut marks on a caribou coxal bone from Cave II.

The specimen (# I5.6.5) is dated to 18,570 ± 110 14C BP (OxA-33777) and shows straight and parallel marks resulting from filleting activity.

Fig 3
Fig 3. New radiocarbon determinations obtained on bone from Bluefish Caves I and II.

The red dot on the map indicates the location of the site. Conventional radiocarbon ages are expressed in 14C BP [70], values are ± one standard error [71]. Calibrations (cal BP) were made using OxCal 4.2 [67] and the INTCAL113 calibration curve [68]. ‘Used’ represents the amount of bone powder pretreated in milligrams. ‘Yield’ represents the weight of collagen or ultrafiltered collagen in milligrams. ‘%Yield’ is the percent yield of extracted collagen as a function of the starting weight of the bone analyzed. ‘%C’ is the carbon present in the combusted collagen and averages 40 ± 2% in the ORAU. Stable isotope ratios are expressed in ‰ relative to vPDB [72] with a mass spectrometric precision of ± 0.2 ‰ for C and ± 0.3 ‰ for N. ‘CN’ is the atomic ratio of C to N and is acceptable if it ranges between 2.9–3.5. aDenote duplicate measurements from the start of the pretreatment chemistry. bSpecimen also identified in previous article [39].

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Grants and funding

Support was provided by Fonds de Recherche Québécois Société et Culture (2015-SE-179537), grant received by AB.

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