The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)

A synthesis of genotype and phenotype reveals the multi-causal nature and complexity of human cranial evolution


1Anthropology, University of Illinois, 2Program in Ecology, Evolution, and Conservation, University of Illinois

March 26, 2015 , Gateway Ballroom 2 Add to calendar

The comparative study of human phenotypic variation among recent and living groups is crucial for evaluating hypotheses of human adaptation. Comparative methods make a series of assumptions about the distribution of genetic similarities among groups and the forces of evolution. Using a combination cranial and whole-genome molecular data in conjunction with a maximum likelihood general hierarchical modeling framework, we compare the goodness of fit of evolutionary models assumed in most comparative studies of human variation. We also investigate models that allow for tests of a variety of hypotheses of the causes of phenotypic evolution against a background informed by genomic variation. Our results show that models of evolution assumed by many comparative studies of human phenotypic variation are poor fits to both phenotypic and genomic data. The goodness of fit of more complex models shows that a combination of random genetic drift and neutral mutation on one hand, and natural selection on the other, is responsible for the evolution of recent human cranial diversity. The effects of environment and gene flow may also be substantial. We show that none of these conclusions could be arrived at using either phenotypic or genomic data alone. The former is too noisy to be of use in reconstructing population history and the latter contains almost no information about the action of natural selection on most phenotypic traits. Washburn’s (1951) call for a synthesis of the study of phenotype and genotype is as timely as ever.

Early parts of this work were completed during a fellowship semester funded by the Center for Advanced Study, University of Illiois, Urbana-Champaign.