Approaches to Estimating Marine Protein in Human Collagen for Radiocarbon Date Calibration

Abstract

ABSTRACT. Determining the appropriate approach to calibrating radiocarbon dates is challenging when unknown and variable fractions of the carbon sample are derived from terrestrial and marine systems. Uncalibrated dates from a large number of human skeletons from Western Cape and Southern Cape locales, South Africa (n = 187), can be used to explore alternate approaches to the marine carbon correction. The approach that estimates theoretically expected minimum and maximum values for marine carbon ("expected") is compared to the approach that estimates observed minimum and maximum values ("observed"). Two case studies are explored, wherein skeletons interred together have non-overlapping conventional 14 C ages. The case from the Western Cape is explored through carbon isotope values; the case from the Southern Cape uses nitrogen isotope values. In both cases, the approach using observed endpoints yields better date calibration results. Analysis of the large sample shows that mean values for estimated dietary % Marine, as calculated using expected and observed protocols, are significantly different. We conclude that the observed protocol is preferred, and that improved measures of the local marine reservoir (R) are needed for this region.

Colonisation of Remote Oceania: New dates for the Bapot‐1 site in the Mariana Islands

“…Petchey et al (2015), however, found that a diet correction using linear extrapolation between terrestrial and marine δ 13 C endpoints, in a similar manner to established protocol for human bone dietary corrections (e.g. Arneborg et al 1999;Dewar & Pfeiffer 2010;Petchey et al , 2014 could be used to determine the appropriate mix between terrestrial and marine 14 C calibration curves for chicken bone (Gallus gallus) from Teouma, Vanuatu. For the Bapot-1 rail bone sample (SANU-11625) we have therefore applied a linear extrapolation methodology using −21‰ and −12‰ δ 13 C endpoints (for the methodology, see Petchey et al 2014).…”

“…Arneborg et al . ; Dewar & Pfeiffer ; Petchey et al . , ) could be used to determine the appropriate mix between terrestrial and marine 14 C calibration curves for chicken bone ( Gallus gallus ) from Teouma, Vanuatu.…”

Stable isotope ecology and human palaeodiet in the northern coast of Santa Cruz (Argentine Patagonia)

“…The surface layer of the world's oceans consists of both contemporary carbon and older 14 C depleted waters brought up from the deep ocean through upwelling. The average 14 C age of the world's ocean surface layers is 405 ± 22 years (Dewar & Pfeiffer, ). In addition to R(t), each region has its own deviation, or local marine reservoir effect (ΔR), based on local mixing of currents and sources of upwelling (Stuiver & Braziunas, ).…”

“…The surface layer of the world's oceans consists of both contemporary carbon and older 14 C depleted waters brought up from the deep ocean through upwelling. The average 14 C age of the world's ocean surface layers is 405 ± 22 years (Dewar & Pfeiffer, 2010).…”

Bioarchaeological Evidence for the Basis of Small Adult Stature in Southern Africa

“…Radiocarbon dates based on human bone collagen can be biased when they come from the skeletons of people who ingested marine protein during life, because marine carbon is older than terrestrial carbon. There are various approaches to estimating the proportion of marine dietary protein (e.g., Dewar and Pfeiffer 2011;Stynder et al 2009), and the magnitude of the marine offset will differ depending on whether the foodstuffs came from the Indian Ocean or the South Atlantic (Benguela) Ocean currents. There is little information available for the latter offset, however, and so we proceed with uncalibrated dates.…”