Testing hypotheses about human adaptive evolution using matched molecular and phenotypic data

Anthropological genetics and paleoanthropology traditionally occupied separate niches in the study of modern human origins, rarely cross fertilizing one another and occasionally adopting adversarial stances. This separation is unfortunate because of the critical interdependence of genetic and morphological approaches to understanding evolution. It is also completely surmountable due to the fact that there is a large body of evolutionary quantitative genetic theory available to study these problems. This dissertation includes a series of three studies demonstrating applications of evolutionary quantitative genetics to the study of the evolution of modern human phenotypes. The first study, addressed estimating the within- and among-region components of variance underlying different aspects of morphological size and shape. Only upper facial shape seemed to deviate from neutral expectations while other aspects of shape and size appear to be evolving neutrally. The second study involved comparing matrices of pairwise interpopulational genetic and phenotypic (cranial) distances in an extension of the comparative method. I used extremes of cold as a selective hypothesis. This allowed me to see which populations and which traits conformed to a neutral model of evolution and which did not. Cranial variation was largely neutral with the exception of measures of cranial breadth and nasal and facial width and height. A single population living in an extremely cold environment accounted for most of the deviations from neutrality. The third project presented a similar test of neutrality applied to the global distribution of skin pigmentation variation as measured by skin reflectometry at the 685nm wavelength. I used the same matrix comparison method as in the second project and incorporated latitude as a variable representing my selective hypothesis. The neutral model of skin evolution was rejected and the main cause of among population differentiation in skin reflectance at the global level appears to be adaptation by natural selection to local conditions consistent with adaptationist hypothesis of the selective importance of UV radiation.