Short-Lived Plant Materials, Long-Lived Trees, and Polynesian ¹⁴C Dating: Considerations for ¹⁴C Sample Selection and Documentation

Abstract

ABSTRACT. For over 2 decades, there have been calls for Polynesian archaeologists to identify radiocarbon samples to taxon and material type, and preferentially date short-lived materials. This stems from recognition that even modest amounts of inbuilt age are problematic in this oceanic region where human settlement dates to the last 3 millennia or less. Despite programmatic statements to this effect, and empirical demonstrations of value, uptake of these practices has been slow. This article suggests that short-lived materials be defined as those with lifespans of 10 yr or less, recognizing that reducing the distance between target event and the dated material is an ongoing aim for archaeology. We identify both short-lived materials that are suitable for dating and long-lived species (>75 yr) that should be avoided given their potential for inbuilt age. Additionally, we suggest that given the destructive nature of 14 C dating there is value to (1) obtain high-resolution photographs of samples prior to analysis, (2) split samples and archive residuals when possible, and (3) routinely report the tools and expertise used in identification. Past and recent dating analyses at a Polynesian site in the southern Cook Islands are used to illustrate how the suggested protocols might enhance current and future studies. We also establish that mature Calophyllum inophyllum, a common coastal tree and valued timber species, has been in the southern Cook Islands for at least the last 700 yr and is likely to be indigenous and long-lived.

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

“…Radiocarbon results of wood charcoal samples may be influenced by inbuilt age if they originate from long‐lived species (Allen & Huebert ), or by “storage age” if the species selected is resistant to weathering and decay, or if stored wood is burned (Schiffer ).…”

Dispersal, Isolation, and Interaction in the Islands of Polynesia: A Critical Review of Archaeological and Genetic Evidence

“…This has shifted the bar Diversity 2017, 9, 37 4 of 21 higher for accepting new results and has been the inspiration for re-dating sites where early dates had been reported. Allen and Huebert [21] have reviewed which plant taxa are likely to yield good results. Others have continued to refine how best to calibrate marine carbon results [22,23], which are especially important given how commonly fish and shellfish are found in Oceania, and how variable the marine calibration is across space.…”

Not just carbon: assessment and prospects for the application of anthracology in Oceania

“…Although the potential of wood charcoal analysis for palaeoecological reconstruction was rapidly recognised, the application of taxonomic identification to archaeological wood charcoal in the Pacific has been influenced by the need to eliminate long-lived species in samples used for radiocarbon dating (see Allen & Huebert 2014;Allen & Wallace 2007;Spriggs & Anderson 1993).…”