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 lifetable 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.

Human age estimation from lower-canine pulp volume ratio based on Bayes’ theorem with modern Japanese population as prior distribution

“…As mentioned above, inverse regression is not appropriate for age estimation unless the age distribution of the target sample is same as that of the reference sample. Since the critique by Bocquet-Appel and Masset (1982) of the conventional regression approach (inverse regression), the Bayesian approach has been a promising methodology for a new ageestimation scheme (Lucy et al, 1996;Buckberry and Chamberlain, 2002;Gowland and Chamberlain, 2002;Storey, 2007;Kimmerle et al, 2008;Konigsberg et al, 2008;Nagaoka et al, 2008;Coqueugniot et al, 2010;LangleyShirley and Jantz, 2010;Thevissen et al, 2010;Nagaoka et al, 2012a, b). The Bayesian approach takes the age distribution of the target population (referred to as prior distribution) into the probability calculation and, therefore, the answer (referred to as posterior distribution) circumvents the above-mentioned problem as it is customized to the target population.…”

Maximum likelihood estimate of life expectancy in the prehistoric Jomon: Canine pulp volume reduction suggests a longer life expectancy than previously thought

“…Since this distribution is unknown (after all this is what we are trying to estimate) an alternative approach, which provisionally assumes some age distribution as the prior probability distribution, has been applied (Bullock, M arquez, Hern andez, & Ruíz, 2013;DeWitte, 2010;Nagaoka, Sawada, & Hirata, 2008;Storey, 2007). The Bayes theorem requires a prior distribution for the calculation, and in a strict sense this should be the age distribution of deaths of the target population.…”

“…The Bayes theorem requires a prior distribution for the calculation, and in a strict sense this should be the age distribution of deaths of the target population. Nagaoka et al (2008) utilized the results obtained by Buckberry and Chamberlain (2002, (2011) demonstrated using known-age samples, this method does not reproduce a true age distribution, but instead produces a distribution that mimics the provisionally assumed prior probability distribution. Buckberry and Chamberlain (2002) assumed a uniform age distribution as a prior, and calculated stage-conditional age distributions of auricular-surface developmental stages according to the Bayes theorem.…”

“…Since this distribution is unknown (after all this is what we are trying to estimate) an alternative approach, which provisionally assumes some age distribution as the prior probability distribution, has been applied (Bullock, M arquez, Hern andez, & Ruíz, 2013;DeWitte, 2010;Nagaoka, Sawada, & Hirata, 2008;Storey, 2007). Therefore, while Nagaoka et al (2008) extended the estimate of Jomon longevity significantly from the previous estimation of $16 years (Kobayashi, 1967) to 31.5 years, their estimate cannot be considered reliable because their results were driven by an a priori assumption of a long life expectancy at age 15 of 40.0 years (calculated by the present authors from Buckberry & Chamberlain, 2002, table 13). Nagaoka et al (2008) utilized the results obtained by Buckberry and Chamberlain (2002, (2011) demonstrated using known-age samples, this method does not reproduce a true age distribution, but instead produces a distribution that mimics the provisionally assumed prior probability distribution.…”

An informative prior probability distribution of the gompertz parameters for bayesian approaches in paleodemography

“…Most of the studies undertaken so far have applied the Bayesian theorem indirectly in estimating age distributions of deaths (Storey, 2007;Nagaoka et al, 2008;DeWitte, 2010;Bullock et al, 2013;Nagaoka et al, 2013). In these approaches, first, the posterior probability distributions of individual skeletal age are calculated by applying the Bayes theorem, and then summed to obtain the (estimated) age distribution of deaths.…”