Utility of the sternum to estimate sex and age
Bruce, Johnathan Scott
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Of the 206 bones that compose an adult skeleton, only a select few are used in the estimation of sex and age. The best indicator of the sex of an adult skeleton is derived from several morphological features of the pelvis. In addition to the pelvis, characteristics of the sacrum, long bones, and skull have been used to estimate sex in adult remains. The most accurate indicators of age-at-death at the present time are related to features of the pubic bone, the auricular surface of the ilium, and the sternal end of the fourth rib. The current project assesses the utility of the sternum for estimating age and sex using two current methods. The two methods in question are those of Bongiovanni and Spradley (2012) for the estimation of sex and Sun et al., (1995) for the estimation of age. The data gathered at the Robert J. Terry Anatomical Skeletal Collection for this study is used to assess the validity and accuracy of the two different methods utilizing a North American population differing from that of Bongiovanni and Spradley (2012). Results showed a high congruence with the results of Bongiovanni and Spradley (2012) in which an overall classification rate of 81.1% was achieved. The cross-validation classifications for males and females were 79.9% and 83.6% respectively and an overall classification rate of 86.7% was achieved using total sternal length (TL). Results also demonstrate that the mean values of sternal index conform to Hyrtl's Law, however the range of values largely overlap, and demonstrates the law's unreliability for sex estimation. Results showed a lack of congruence with the Sun et al., (1995) method reaching a classification rate for exact age estimates of 14.4%. Overall, the utility of the human sternum for sex estimation seems promising and practically simple. The utility of the human sternum for age estimation merits further research into methods that might provide higher classification rates, however, at this time no methods seem worthwhile.