Did the Jomon people have a short lifespan? Evidence from the adult age-at-death estimation based on the auricular surface of the ilium

Abstract

The demography of the Jomon people was first systematically investigated by Kobayashi ([1967] Journal of the Faculty of Science, The University of Tokyo, Section V, 3: 107-162). His life-table analysis indicated that Jomon life expectancy at the age of 15 was only 16 years. However, recent advances in palaeodemography have questioned whether the reconstruction of demographic parameters from skeletons actually reflects the real mortality patterns of past populations. The purpose of this study is to test the hypothesis that palaeodemographic data from skeletal remains represent an appropriate adult mortality profile. If the hypothesis is the case, the mortality profile of the Jomon people implied the heavy work-load resulting in the unusually high mortality schedule. If it is not the case, on the other hand, Kobayashi's data had been distorted by the errors of adult age-at-death estimation. This study examined well-preserved auricular surfaces of 86 individuals, which are individuals aged 15 years and above. Age estimation of the auricular surfaces was performed using two techniques: the original method of Lovejoy et al. ([1985] American Journal of Physical Anthropology, 68: 15-28) and the revised method of Buckberry and Chamberlain ([2002] American Journal of Physical Anthropology, 119: 231-239). The results indicate important findings on the mortality profile of the Jomon people. First, the revised estimation has older age distributions, with the majority of individuals over 65 years of age. Second, the revised estimation increases the life expectancy at the age of 15 from 16 years to 32 years. The present data lead to the conclusions that the revised method improves the accuracy of age estimation for elderly adults, and that the Kobayashi's estimation does not represent the real mortality profile. These findings will have great effects on the life history reconstruction of the Jomon people. © 2007 The Anthropological Society of Nippon.