Variation in the human bicondylar angle

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.