The Evaluation and Refinement of Nonmetric Sex and Ancestry Assessment Methods in Japanese and Thai Individuals

As Submitted By Proposer: Subsequent to deaths resulting from natural disasters, armed conflicts, and homicides, the identification of decedents is paramount and depends on the accuracy of the scientific methods employed in the biological profile (sex, age, ancestry, and stature of skeletonized remains). Accurate biological profile methods require that they be developed, validated, and refined on contemporaneous skeletal assemblages that share a genetic history with the decedents. However, most biological profile methods were developed in North America on individuals of African and European descent, and it is unlikely that such methods can generate accurate biological profiles for Asian individuals living in the U.S. Moreover, Native Americans historically served as biological proxies for Asians due to their shared genetic history, resulting in the assumption that Native Americans and Asians share nonmetric skeletal features, including a less sexually dimorphic skeleton compared to non-Asian groups and a unique suite of cranial traits that can be used to ascertain ancestry. As the population of Asian groups in the U.S. is expected to increase, the continued reliance on methods developed from non-Asian populations is especially problematic in forensic contexts where Asian remains are likely to be recovered (i.e., large U.S. cities and mass disasters). The current study will statistically test and refine the methods used to visually assess nonmetric sex from cranial and postcranial remains, and establish nonmetric cranial trait frequencies for modern adults in documented anatomical collections in Japan (Jikei University, n=200) and Thailand (Khon Kaen University, n=700; Chang Mai University, n=120). As sex is reliably determined from the presence or shape of traits on the skull, clavicle, humerus, and pelvis, these traits will be assigned an ordinal score based on their robust or gracile expression. The scores and documented sexes will be analyzed statistically to identify the traits that best indicate male or female, while testing the hypothesis that Asian populations exhibit reduced sexual dimorphism. Additionally, nonmetric cranial traits commonly used to identify Native Americans will be scored to test the hypothesis that Japanese and Thai individuals differ from Native Americans and each other in their trait expressions and frequencies. The continued refinement of nonmetric sex and ancestry assessment methods is of utmost importance in the current judicial climate, which is dictated by the Daubert ruling of 1993 and requires rigorous testing of scientific methods. This research will provide revised, population-specific methods to improve the accuracy in identifying East and Southeast Asian individuals living in the U.S. ca/ncf