Human facial diversity is substantial, complex, and largely scientifically unexplained. We used spatially dense quasi-landmarks to measure face shape in population samples with mixed West African and European ancestry from three locations (United States, Brazil, and Cape Verde). Using bootstrapped response-based imputation modeling (BRIM), we uncover the relationships between facial variation and the effects of sex, genomic ancestry, and a subset of craniofacial candidate genes. The facial effects of these variables are summarized as response-based imputed predictor (RIP) variables, which are validated using self-reported sex, genomic ancestry, and observer-based facial ratings (femininity and proportional ancestry) and judgments (sex and population group). By jointly modeling sex, genomic ancestry, and genotype, the independent effects of particular alleles on facial features can be uncovered. Results on a set of 20 genes showing significant effects on facial features provide support for this approach as a novel means to identify genes affecting normal-range facial features and for approximating the appearance of a face from genetic markers.

Ethnobiologists debate whether folk biological classifiers are natural historians attending primarily to the morphology of organisms or are pragmatists concerned primarily with utility. We argue that this question is best understood as a problem in intracultural variation: the relative importance of form and function depends on who is asked to judge the similarity of organisms as well as how they are asked to judge it. We find that expert fishermen judge similarities among fish on both functional and morphological criteria, while novices judge on morphological criteria alone and thereby approach the scientific classification of fish more closely than experts. Experts also vary more than do novices, presumably because they control more different kinds of knowledge on which to base a similarity judgment.

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The feeding niche and the body size of any species are fundamental parameters that constrain the evolution of many other phenotypic characters. Moreover, previous work has shown that body size and diet are correlated, as a consequence of the negative allometry of metabolic rate. Unfortunately, the precise form of the association between body size and diet has never been specified, principally because no suitable cross-species measure of diet has been advanced. Here we develop a measure of diet that is sensitive over the whole spectrum of primate feeding niches, and use this measure to define the relationship between body size and diet for a sample of 72 primate species. Subsequently, we present several examples of how behavioral and ecological hypotheses can be tested by examining the extent to which particular species deviate from the general diet-body size pattern.