PAPER ANTHROPOLOGY Allysha Powanda Winburn , Ph.D. Validation of the Acetabulum As a Skeletal Indicator of Age at Death in Modern European-Americans †,‡ ABSTRACT: Progressive changes in the acetabulum have been used in modern skeletal age estimation, but they have not been completely understood. If their age correlations are weakened by the influence of factors like physical activity and obesity, acetabular changes should not be used for age estimation. To investigate their utility for aging, the acetabular variables of Rissech et al. (2006) were analyzed in 409 modern European-Americans (Bass Collection, Tennessee). Correlation tests assessed potential associations between acetabular data, osteoarthritis scores (collected per Jurmain, 1990), and documented demographic information (age, body mass index [BMI], metabolic intensity of physical activi- ties). Acetabular changes had statistically significant, positive correlations with osteoarthritis (p < 0.001 in most joints/regions) and age (p < 0.001), indicating their degenerative nature and relevance for age estimation. Acetabular changes showed no associations with BMI or metabolic values, suggesting resistance to obesity and activity effects. These results suggest that acetabular degeneration is a valid skeletal age- at-death indicator. KEYWORDS: forensic science, forensic anthropology, age estimation, pelvis, skeletal degeneration, arthritis, obesity, physical activity The acetabulum has been a focus of age-estimation research for over a decade, and several acetabulum-based aging methods have been proposed (1–3). However, the progressive changes that occur in the acetabulum remain poorly understood. These changes may constitute skeletal metamorphoses (akin to the for- mation of the ventral rampart of the pubic symphysis), which are generally believed to be linked with age. Alternately, acetab- ular changes may represent osteoarthritis (OA)—generally viewed as degenerative, less strongly correlated with age, and more influenced by factors like physical activity and obesity. This research investigated the nature of progressive changes in the acetabulum. It aims to determine whether acetabular changes are metamorphic or degenerative, ascertain whether they are valid indicators of age at death, and scrutinize the overall utility of a dichotomous, “metamorphic vs. degenerative” approach to age estimation. By focusing on the skeletal biology underlying acetabular changes, this research contributes to an understanding of acetabular age progression that will enhance future method testing and validation. Before acetabular aging methods continue to be developed and refined, the fundamental question of whether this joint surface is a valid age indicator must be answered. Background Accurate and precise methods of skeletal age-at-death estima- tion are vital to the generation of the biological profiles that enable individual identifications. Broad age intervals contribute little to the elimination of potential matches from the universe of missing-persons, while narrow intervals may exclude the correct missing-person from consideration. Still, adult age estimation remains challenging. Forensic anthropologists frequently examine joint surfaces to inform their adult age estimates (1–42). All joints change with age, but some exhibit metamorphic change, while others exhibit degenerative change (39). Metamorphic skeletal changes occur after the attainment of skeletal maturity but independent of skeletal degeneration. They are often portrayed as more relevant to age estimation than degenerative changes, since the latter pro- cesses are complicated by intra-individual variation and inter- individual differences—both hereditary and environmental (e.g., nutrition, bone density, mechanical loading, hormonal influences [39,43,44]). The degenerative processes that complicate adult age estimation can become more pronounced and variable over an individual’s lifetime, and this trajectory effect (45) can trans- late to further-decreased accuracy with advancing age (43,46; cf. 47). Thus, age estimates for elderly adults are often more diffi- cult to achieve, less accurate, and less precise than age estimates for younger adults, and anthropological aging methods tend to underestimate age in the oldest individuals (46,48,49). Yet, due to advances in health care and standards of living, modern individuals are more likely than past peoples to reach 1 Department of Anthropology, University of West Florida, 11000 Univer- sity Parkway, Bldg. 13, Pensacola, FL 32514. Corresponding author: Allysha Powanda Winburn, Ph.D. E-mail: awinburn @uwf.edu † Presented in part at the 70th Annual Scientific Meeting of the American Academy of Forensic Sciences, February 19-24, in Seattle, WA. ‡ Financial support for this study was provided by the National Institute of Justice Graduate Research Fellowship Program in Science, Technology, Engineering, and Mathematics (Grant #: 2015-R2-CX-0009) and the Univer- sity of Florida Graduate School Doctoral Research Travel Award. Received 25 July 2018; and in revised form 8 Oct. 2018; accepted 13 Nov. 2018. 1 © 2018 American Academy of Forensic Sciences J Forensic Sci, 2018 doi: 10.1111/1556-4029.13972 Available online at: onlinelibrary.wiley.com