Quantitative traits in relation to population structure: why and how are they used and what do they imply?

I describe the basic ingredients of a population structure analysis and the rationale for using polygenic quantitative traits in such analyses. The complexity of inheritance and the population dynamics of quantitative traits, however, imply that inferences regarding population structure based on such traits must be evaluated with appropriate cautions. Although many studies of quantitative traits in relation to population structure analysis underscore the importance of gene flow between subpopulations, I show that the role of selection in the evolution of a quantitative trait and its relationship to the inferred population structure cannot be overlooked. Finally, I review some recent advances in human quantitative genetic methodologies that can be used profitably in population structure analysis.