Doctoral Dissertation Research: Improved Skeletal Age-at-Death Estimation and Its Impact on Archaeological Analyses

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Age-at-death estimates from skeletal remains are essential for archaeological studies of human longevity, mortality patterns, population growth, disease experience and mortuary practices, as well as medicolegal identifications of missing persons, crime victims, migrant border deaths, and war-crime victims. Despite over a century of development, the accuracy (estimated and actual age correspondence) and precision (age interval length) of adult age estimates produced by existing methods are insufficient to reach these ends. That means much current understanding of the age-structure of past populations, long-term population trends, pathogen load and its effect on human hosts, and human longevity may be seriously flawed by age-estimation error. In response to this pressing theoretical and practical need, an international research team that includes Dr. George Milner and his doctoral student Sara Getz (Penn State University) are developing a method to produce more accurate, precise, and unbiased skeletal age estimates for the entire adult lifespan, building on their earlier statistical procedure (Transition Analysis, TA). This ongoing work will significantly reduce age-estimation error, describe and quantify skeletal variation, and refine statistical methods. It involves a fundamental shift from assessing only a few skeletal characteristics with simple statistics to analyzing traits throughout the skeleton using sophisticated statistical methods to extract the most information possible from age-related changes in bones. This project will validate the newly expanded TA method on a large number of modern known-age European skeletons, and then apply the procedure to two large medieval and early modern samples as a proof of concept for archaeological applications. At the conclusion of the project, revised TA will be disseminated as a free, downloadable, and easy-to-use program and illustrated scoring manual. Data will be maintained and made available for other researchers' use. The project PI and Co-PI will train students (undergraduate and graduate) and professionals through peer-reviewed publications, professional meeting presentations, and invited lectures and workshops.Validation on numerous known-age European skeletons will demonstrate the increased accuracy and precision of revised TA. This focused study is the first step in expanding the research team?s method to a wide range of geographically diverse populations. After validation, two urban cemetery samples from the Danish city of Horsens - Ole Worms Gade (1100 -1500 CE) and Monastery Church (1500 -1800 CE) - will be used to investigate the potential implications of improved age estimates for our understanding of important social and demographic trends over time, such as changes in migration and adult life expectancy. This application will demonstrate how better skeletal data can bridge the gap between archaeological and historical sources. In particular, it will provide information about the characteristics of past populations that cannot be obtained through historical documents or from skeletons where ages were estimated using standard methods.