Absolute and relative dating of human remains in a Bahamian sinkhole (Great Cistern, Abaco)

The Little Bahama Bank was likely the last island group colonized by the Lucayan natives in the tropical North Atlantic, but preserved Lucayan remains are rare from this region. Furthermore, the Lucayan diet included both marine and terrestrial contributions, which must be considered when calibrating conventional radiocarbon results from human remains into Common Era (CE) calendar years. Here we present a new discovery of Lucayan remains (proximal epiphysis of a right tibia) identified within a sinkhole on Great Abaco Island in the northern Bahamas, which was preserved in the extremely well-dated sedimentary infill (dated with 22 independent radiocarbon ages). The age of the human tibia was estimated through both the associated stratigraphy (relative age), and direct radiocarbon dating of the bone (absolute age). The direct age of the bone was calibrated by using a two-endmember mixing model to estimate the average proportion of marine versus terrestrial contributions to this individuals’ diet using the δ 13C value of the bone collagen and applying a local ΔR value for regional aquatic settings. Absolute dating places the age of the remains from Great Cistern between 1255 and 1340 CE (2σ, probability: 0.89). Applying the same mixing model to the previously discovered remains from Sawmill Sink on Great Abaco Island indicates those remains are in fact 100 to 200 years younger than the previous estimate with internment likely occurring between 1110 and 1290 CE (2σ, probability: 0.95).