A test of the chronological features that determine age changes on the auricular surface of the ilium as an estimation of age at death

Abstract

The study of age changes in the human pelvis has long been at the core of research in human osteology. Particularly, studies have focused on joint surfaces as the age during the lifetime of an individual. This study examines age changes in the posterior ilium, specifically the auricular surface. The auricular surface is defined as the "semi-lunar "sacral articulation on the medial surface of the ilium. A special focus is placed on the assessment of a previous aging technique applied to the auricular surface and the posterior ilium (Lovejoy et al. 1985). A second objective addresses the potential refinement of the proposed age groups defined by Lovejoy et al. (1985). Few studies have yet to test the use of qualitative scoring system on the auricular surface. This study was conducted using a sample of 102 Black females from the Hamann-Todd collection at the Cleveland Museum of Natural History. Both the left and right auricular surfaces were examined bringing the total number of surfaces recorded to 204. In addition to qualitative observations of the surfaces six measurements of the auricular surface were recorded to determine if the size and shape of the surface changes with age. To test age effects separate t-tests were applied to their right and left size dimensions of the surface to test for right and left symmetry and size differences between the surfaces of young and old specimens. The findings presented here suggest that the nature of qualitative morphological features change with age. As age increases the sacroiliac joint becomes less mobile and degenerative changes on the auricular surface that include lipping on the apical border increase, which may affect the shape and size of the auricular surface as age increases. The t-test results indicate that there are no significant differences between the left and right auricular surfaces. Age according to the t-test also indicates that there are no significant differences from young to old age, with the exception of one measurement. The inferior auricular surface length (IFASLT) is the minimum width of the auricular surface between the apex and the posterior border of the auricular surface. The difference in this measurement from young to old is affected by the increase in apical and retro-auricular activity. As retro-auricular activity increases it affects the posterior border of the auricular surface causing the border to become less pronounced. The apex is affected by the increase of lipping as age increases. Increasing age causes this measurement to be slightly higher than in younger individuals, whether as a result of activity or less clarity in the measurement as age increases is unknown. The findings presented here suggest that the nature of qualitative morphological features change with age. To test these findings a chi-square analysis was applied to determine if the presence and absence of features are determined by age. Results concluded that all features, with the exception of porosity had significant results. Based on these results a revised age phase system limited to four phases is presented, which represents a less precise, but more consistently reliable indicator of age than that of the eight phase system proposed by Lovejoy et al. (1985). The findings suggest that morphological features are best seen within the decade rather than within half a decade, suggesting that it is better to include broader age ranges in order to account for a more accurate age estimation of an individual.