The influence of climate and population structure on East Asian skeletal morphological variation
Abstract
Objectives: Recent studies have shown that global variation in body proportions is more complex than previously thought as some traits formerly associated with climate adaptation are better explained by geographic proximity and neutral evolutionary forces. While the recent incorporation of quantitative genetic methodologies has improved understanding of selection due to climate in Africa, Europe, and the Americas; Asia remains underrepresented in recent and historic studies of body form. As ecogeographic studies tend to focus on male morphology, potential sex differences in features influenced by climate and magnitude of selection remain largely unexplored. Materials and Methods: Skeletal measurements encompassing the dimensions of the skull, pelvis, limbs, hands, and feet were collected from male (N = 459) and female (N = 442) remains curated in 13 collections across seven countries in East Asia (N = 901). Osteological data were analyzed with sex and minimum temperature as covariates adjusted by autosomal SNP population genetic distance using univariate Bayesian linear mixed models, and credible intervals were calculated for each trait. Results: Analysis confirmed a relationship between specific traits and climate as well as the magnitude of response in both sexes. After accounting for genetic distance between populations, greater evidence for selection was found acting upon postcranial traits, with the influence of climate on the skull limited primarily to breadth measurements. Larger body size is selected for in colder climates with most measurements increasing with decreased temperature. Selection did not always act upon the same traits in males and females or with the same intensity for both sexes. Discussion: The varied directional selection pressure of climate for different regions of the skeleton and between the sexes underscores the necessity of future ecogeographic research to holistically evaluate body form and to look for sex-specific patterns to better represent population responses to environmental stresses.
Degree
Ph. D.