Estimation of skeletal adult age distribution of Okhotsk people in northern Japan

The demographic structure of prehistoric hunter-gatherer societies has contributed to our understanding of the life history patterns of past human populations. The purposes of this study are to examine the human skeletal remains associated with the Okhotsk culture, to estimate age-at-death distribution using the Buckberry–Chamberlain system of auricular surface aging and the Bayesian approach, and to discuss whether paleodemographic estimates can yield an appropriate mortality profile of prehistoric hunter-gatherers in Japan. The application of the Bayesian theorem to the age-at-death estimation was based on the modern Japanese and Spitalfields known-age collections, assuming uniform, reference, and model prior probabilities. The age distributions of the Okhotsk had low proportions of young adults and high proportions of elderly adults. The results indicated that 24.4–51.3% of individuals were above the age of 55 years. The newly employed technique of the Bayesian estimation yielded the age distributions with significant numbers of elderly individuals, which are contrary to usual paleodemographic estimates. The results of this study suggest direct and plausible evidence of demographic traits in the Okhotsk people and allow us to reveal the mortality schedules of the prehistoric hunter-gatherers that otherwise could not be reconstructed from historical or ethnological records.