Differential reliability of 14C AMS ages of Rattus exulans bone gelatin in south Pacific prehistory

Analysis of assemblages of AMS radiocarbon determinations of Rattus exulans bone gelatin samples collected in the south Pacific (New Zealand and Norfolk Island) shows that results from both archaeological and natural sires have an inverse correlation of radiocarbon age with sequence of processing, particularly in IGNS data. Consideration of potential causes of this variation, including differential dietary effects and sample degradation, provides no general explanation. It is hypothesized that laboratory processing of rat bone samples improved with experience. Taken into account, this proposition brings rat bone gelatin radiocarbon ages into line with prevailing archaeological and palaeoenvironmental opinion about ages of human colonisation and the concurrent introduction of Rattus exulans to the southern islands of Polynesia about 800 B.P. Problems remain in the radiocarbon dating of rat bone, however, and the reliability of determinations is currently uncertain.