Historically, metric and morphological standards used in forensic anthropology and bioarcheology were derived from individuals of European and African descent and ancient Native Americans. However, it is unlikely that these standards can be accurately applied to modern Asian populations. Due to different population histories, it is hypothesized that ancient Native American and modern Thai individuals are metrically distinct. This study investigates the metric differences in sexual dimorphism between 102 Native American (American Museum of Natural History) and 100 modern Thai (Khon Kaen University) individuals 17 to 96 years of age. A total of 28 cranial, 9 mandibular and 58 postcranial measurements were compared between Native American and Thai individuals. Subsequently, select measurements were tested in Spradley and Jantz's (2011) American Black and White sex estimation equations to see how equations derived from non-Asian populations perform on Native American and Thai individuals and to ascertain if population differences exist in the expression of sexual dimorphism. Lastly, population-specific logistic regression equations were developed for both sample populations. Using logistic regression equations and discriminant function analyses - quasi-ordinary least squares, the Native American and Thai groups are significantly different in the expression of sexual dimorphism. Further, Spradley and Jantz's (2011) equations often fail to correctly classify Native American and Thai individuals. In particular, the equations derived from American Black and White individuals frequently classified modern Thai and Native American males as females. Conversely, three American White equations and eight American Black equations classified more females as males for both populations. Therefore, the metric sex estimation methods developed on non-Asian populations do not adequately classify Native American and Thai individuals. The application of sex estimation methods developed on non-Asian populations results in reduced discriminatory power because Native Americans and Thais are less sexually dimorphic than African and European American individuals. The equations developed on the modern Thai sample correctly classified 71.1 - 96.0% of the individuals, while those developed on the Native American samples correctly 78.1 - 97.8%.

The use of the Daubert Standard in court proceedings has highlighted the need to substantiate scientific findings or claims beyond simply accepting the word of a respected expert. The concept of postmenopausal masculinization of the skull in female crania falls into this category. Dr. Walker references this concept in several articles but there is no research to support this hypothesis. This project examines the theory of postmenopausal masculinization of female crania from several perspectives, using the visual sex estimation method set forth in Standards for Data Collection from Human Skeletal Remains edited by Jane E. Buikstra and Douglas H Ubelaker, photographic seriation of these sex estimation traits, and metric measurements in conjunction with Fordisc 3.1. A sample of 395 crania from the Hamann-Todd Collection at the Cleveland Museum of Natural History was analyzed using all three of these methods to determine if there was a pattern of masculinization in the postmenopausal female sample. The average age for the onset of menopause in the United States is 50, thus there should be an increase in "masculinization" observable through more rugged sex estimation traits, a higher number of females 50 or over being found below the midpoint in photographic seriations of sex estimation traits, and an increase in Fordisc 3.1 sex identification misclassifications in females in this age category. The results of the analyses revealed that there were statistically significant differences between ancestry groups, the sexes, and in some cases, age-groups. The results of this research indicate that though there are some differences between comparison groups, there does not appear to be a cohesive pattern of masculinization in female crania at or after the average age of onset of menopause. Human variation is endless, and even in areas of the skeleton for which it has been established that there is a significant degree of sexual dimorphism, there will be individuals who do not fit neatly into a binary conception of sexual divergence. Though these individuals may be misidentified as the opposite sex using one or all of the methods utilized in this project, this falls short of being classified as a part of the menopausal process in females.