Race and ethnicity as biological constructs.

For some time, biologists and anthropologists have overwhelmingly rejected the partitioning of modern humans into biological "races." An examination of recent human evolutionary history suggests that the zoological definition of race, based on significant genetic differences, cannot be legitimately applied to contemporary humans. Extensive past hybridization, plasticity of the human phenotype, the presence of ecotypes, the lack of extensive molecular information, and the lack of longitudinal multigenerational evaluations of diverse groups contribute to ambiguity in taxonomic assignment. Although biological aggregates do exist, they represent variation below the subspecies level, and, as such, are much more tenuous over evolutionary time. The persistent reference to quasibiological constructs such as ethnicity and race in the lay and scientific literatures requires that ethnicity be scrutinized for possible biological dimensions. The Diop model of ethnicity suggests that at least three components contribute to its formation: a historical factor, a linguistic factor, and a psychological factor, each of which can be examined for possible biological dimensions. Presumed biological affinities may allow certain groups to expand and extend their collective history and amplify their kin networks, possibly improving group biological fitness. Individual and group initial language of acquisition may influence brain physiology and organize the template for interpretation and behavior, creating greater consistency of response across otherwise divergent biological aggregates. Psychological continuity in particular behavioral traits, particularly repetitive multigenerational responses, may have an adaptive aspect at the group level. While ethnicity remains primarily a sociocultural category, it has biological precursors, parameters, and consequences for both individuals and groups. The genetic components of these biological dimensions remain to be identified and quantified.