Higham, Thomas F.G.Ramsey, Christopher BronkPetchey, FionaTompkins, C.Taylor, M.Higham, Thomas F.G.Ramsey, Christopher BronkOwen, Clare2025-12-082025-12-082004Higham, T., Ramsey, C. B., Petchey, F. J., Tompkins, C., & Taylor, M. (2004). AMS radiocarbon dating of Rattus Exulans bone from the Kokohuia Site (New Zealand). In Higham, T., Ramsey, C. B., & Owen, C. (Eds.), Radiocarbon and Archaeology Fourth International Symposium (pp. 135-151). Oxford University School of Archaeology.97809478166500947816658https://hdl.handle.net/10289/17810We AMS radiocarbon dated rat bones (Pacific rat (Rattus exulans)) from the archaeological site of Kokohuia, in Northland, New Zealand. An initial series were up to 1200 years too old, but the reason for the offset remained obscure. We considered dietary foodwebs, post-depositional contamination and taphonomy as possible explanations. None provided robust answers. Finally, we identified a laboratory-related error, in which a small amount of old carbon derived from humectants (glycerin) used to moisten ultrafilters prior to the extraction of bone collagen, had become incorporated in the dated collagen. The glycerin humectant was present in amounts averaging 30-40 mg C per ultrafilter, which ordinarily is too small to significantly affect single dates obtained on bone collagen, but was significant in the case of small rat bones. Redating of bones from identical contexts produced a series of results which were within agreement with the age of the site as determined from other materials, including short-lived identified charcoal, and marine and estuarine shell. These results sound a warning for dating very small bone samples, and emphasise the need to consider all possible contaminants derived from laboratory preparation and chemical processing background. In addition, it emphasises the requirement for utilising standard samples of identical type (eg, bone, charcoal, wood etc) which range from young (1-2 half-lives) to background in age, as well as low and high sample mass, as QA laboratory checks on reproducibility (Bronk Ramsey et al., in press).enThis is an author's accepted manuscript of a conference paper presented at the Radiocarbon and Archaeology Fourth International Symposium. © 2004 Oxford University Press.Conference Contribution