Appraisal of radiocarbon dating of kiore bones (Pacific rat Rattus exulans) in New Zealand

The radiocarbon dating of bones found in New Zealand of the Pacific rat (Rattus exulans) has been a controversial subject for some time, mainly because many of the dates are much older than expected and imply colonisation of the islands at an earlier time than suggested by archaeological evidence. Also, the dating of Pacific rat bones from two archaeological sites appears inconsistent with and older than other dates from these sites. Part of the controversy has settled on the validity of the dating methodology, and it is the case that most dates have been measured by only one laboratory, and that the ability to date such small samples is only fairly recent. This paper examines the dating methodology used, and considers possible causes for discrepancies in the dates.