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Objectives Humans generally comply with the ecological rule of Allen (1877), with populations from tropical environments exhibiting body proportions in which limb segments are long relative to trunk height compared to temperate groups. This study tests whether ecogeographic differences in intralimb proportions are identifiable among two modern fetal samples of differing ancestry. Materials and methods Data are derived from radiographic measurements of long bone diaphyseal length and crown-heel length (CHL) of contemporary, spontaneously aborted fetuses of African Americans ("black") of assumed African (tropical) ancestry and European Americans ("white") of assumed European (temperate) ancestry (n = 184). Population individual limb elements, brachial, and crural indices are compared via analyses of covariance (ANCOVA). Potential patterns of divergent allometric growth are quantified through principal components analysis (PCA). Results African ancestral distal limb elements were consistently, albeit slightly, longer than those of European ancestry, relative to CHL. None of the ANCOVA interactions with ancestry are statistically significant for limb indices. The radius was the only single element that displayed a statistically significant ancestry effect (p = 0.0435) equating to a 1 mm difference. PCA highlights that upper limbs demonstrate negative allometry and lower limbs demonstrate positive allometry with sample-specific multivariate growth patterns being nearly identical. Differences in growth allometry late in gestation make little contribution to observed differences in adult limb proportions. Discussion No statistically significant ecogeographic patterns were appreciated among intralimb proportions between these groups during the fetal period. This study contributes to a greater appreciation of phenotypic plasticity, ecogeographic variation in ontogeny, and the evolution of modern human diversity.

Objectives Human sexual dimorphism is frequently assessed through skull and pelvic size and shape. Researchers suggest that climatic variation and the associated stress may be significant factors in sexual dimorphism's etiology. However, little research has specifically investigated climatic effects on nonmetric skeletal indicators of sex. To further appreciate the plasticity of human biology, a comparative study of standard skull and pelvic nonmetric sex indicators is presented. Methods A Native Alaskan archeological sample (n = 104) and a component of the Terry collection (n = 99) represent populations originating from different climatic environments in recent history. These sex-balanced groups are compared through Tukey-Kramer's method and Greene's t-test to determine any variation in degree of sexual dimorphism within and between samples. Results The results reinforce the complex and multifaceted relationship between climate and sexual dimorphism. The Terry sample demonstrated a greater degree of sexual dimorphism with statistically significant differences in robusticity of the mastoid process and nuchal crest compared with the Native Alaskans. A more "male" morphotype and reduced dimorphism are appreciated in the pelves of Native Alaskans than the Terry sample. Conclusions This research highlights a reduction in sexual dimorphism in populations under greater climatic stress and contributes to the production of more accurate skeletal assessments in future investigations. Discussion of confounding factors suggest more research is necessary to untangle climate and human morphology's complex relationship. This study contributes to a greater appreciation of human biological plasticity, ecogeographic variation, and the evolution of modern human diversity.

Objectives Investigations of the human femoral bicondylar angle have largely focused on interspecific differences and intrapopulation variation. This analysis assesses the range of variation in the bicondylar angle in humans across four populations, examining the effects of population, sex and age. Materials and Methods The bicondylar angle was assessed in four sex- and age-balanced adult skeletal samples—modern Terry Whites and Blacks and archaeological South Dakota Arikara and Native Alaskans. The overall range of variation was assessed, and variation specific to population, sex, and age analyzed through ANOVAs and post hoc Tukey's honestly significant difference tests. Results A one-way ANOVA highlights a significant effect of population on bicondylar angle; however, the only significant difference occurs between the Terry White and South Dakota Arikara samples. Sex displays a significant effect for the total pooled sample; yet, within population, the effect of sex is significant only among South Dakota Arikara. Age also has a significant effect on bicondylar angle in the total sample; however, the interaction between age and population is not significant. Conclusion The results highlight the degree of variation in the bicondylar angle that exists intraspecifically. Differing degrees of variation due to sex suggest that sexual dimorphism is not universal in the human bicondylar angle. Furthermore, the broad impact of age on this feature is discussed, including the potential for plasticity through adulthood. By recognizing and explicitly examining morphological features that vary in human populations, we can appreciate the origins of variation and its implications for locomotor function, human diversity and evolutionary relationships. Am J Phys Anthropol 160:334–340, 2016. © 2016 Wiley Periodicals, Inc.