Social diversity in humans: implications and hidden consequences for biological research.

Humans are both similar and diverse in such a vast number of dimensions that for human geneticists and social scientists to decide which of these dimensions is a worthy focus of empirical investigation is a formidable challenge. For geneticists, one vital question, of course, revolves around hypothesizing which kind of social diversity might illuminate genetic variation-and vice versa (i.e., what genetic variation illuminates human social diversity). For example, are there health outcomes that can be best explained by genetic variation-or for social scientists, are health outcomes mainly a function of the social diversity of lifestyles and social circumstances of a given population? Indeed, what is a "population," how is it bounded, and are those boundaries most appropriate or relevant for human genetic research, be they national borders, religious affiliation, ethnic or racial identification, or language group, to name but a few? For social scientists, the matter of what constitutes the relevant borders of a population is equally complex, and the answer is demarcated by the goal of the research project. Although race and caste are categories deployed in both human genetics and social science, the social meaning of race and caste as pathways to employment, health, or education demonstrably overwhelms the analytic and explanatory power of genetic markers of difference between human aggregates.