Sexual Dimorphism and Socioeconomic Status: Comparison between Migrant and Non-migrant Populations
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Variation in sexual dimorphism is related to average body size differences and limb proportions between males and females between and within populations (Charisi et al. 2011). The Female Buffering Hypothesis suggests that expression of sexual dimorphism relies on male susceptibility to impairment in long bone length during episodes of stress, while females are buffered from the same conditions due to reproductive demands (Charisi et al. 2011; Frayer and Wolpoff 1985; Gray and Wolfe 1980; Greulich 1951; Rickland and Tobias 1986; Stini 1969; Stinson 1985). This study evaluates the degree of sexual dimorphism to determine if differences in the expression of sexual dimorphism exist between a migrant and non-migrant sample from Mexico. The sexual dimorphism index (SDI) was calculated for 26 postcranial measurements in a migrant group of United States–Mexico border crossing fatalities from Tucson, Arizona (n=119), non-migrant groups from the state of Hidalgo in Mexico (n=44), and American White individuals from the Forensic Anthropology Data Bank (FDB) (n=92). A Multivariate Analysis of Variance (MANOVA) indicated no significant differences in the expression of sexual dimorphism between the three samples, suggesting that sexual dimorphism cannot be used as a proxy to estimate the health and nutritional status of a population (Eveleth 1975). Results from an Analysis of Variance (ANOVA) with a Tukey test indicated no significant difference on long bone length dimensions between migrant and non-migrant samples. Because no significant differences were found in the expression of sexual dimorphism between the three samples, possible environmental factors affecting the variation seen in most of the measurements were examined. Significant differences in long bone length, articular surfaces, proximal and distal ends and the midshaft of long bone lengths were found when the migrant and non-migrant samples were compared to the American White samples. Potential explanations for the significant differences can be attributed to the interaction of diet, socioeconomic status, and division of labor. Furthermore, the observed differences in long bone length when comparing American Whites to both Mexican samples demonstrate the need for population specific methods for the identification of individuals considered Hispanic.