This paper examines the relationship between alveolus eruption, eruption stage the of Japanese archaeological pig teeth, and the actual age at death based on the analysis of modern captive wild boars which are the progeny of trapped and confined wild boars kept for less than several generations. The timing of molar eruption for both maxillae and mandibles for both captive and wild boar populations was also investigated. The results indicate that the attrition pattern in molars varied between individuals with exactly the same age at death and even between those that were kept under the same conditions and diet. The variation in the eruption pattern of maxillae and mandibles was also observed, with molars erupting relatively earlier in maxillae compared to the mandibles in both captive and wild populations. It became clear that separating “M2 erupted” individuals and “M3 erupting” individuals into different age group as done by many researchers should be avoided because of overlap. A method based on the eruption status of the last tooth of the tooth row was established and then applied to archaeological pig material excavated from the Haneo and Torihama shell-middens, Japan, both dated to the Early Jomon Period (ca.7000 to 5500BP). Two Jomon assemblages reveal a different pattern, with a relatively higher frequency of younger individuals represented at Torihama and a relatively higher frequency of older individuals at Haneo.