Physical anthropology, branch of anthropology concerned with the origin, evolution, and diversity of people. Physical anthropologists work broadly on three major sets of problems: human and nonhuman primate evolution, human variation and its significance, and the biological bases of human behaviour. The course that human evolution has taken and the processes that have brought it about are of equal concern. In order to explain the diversity within and between human populations, physical anthropologists must study past populations of fossil hominins as well as the nonhuman primates. Much light has been thrown upon the relation to other primates and upon the nature of the transformation to human anatomy and behaviour in the course of evolution from early hominins to modern people—a span of at least four million years.
The processes responsible for the differentiation of people into geographic populations and for the overall unity of Homo sapiens include natural selection, mutation, genetic drift, migration, and genetic recombination. Objective methods of isolating various kinds of traits and dealing mathematically with their frequencies, as well as their functional or phylogenetic significance, make it possible to understand the composition of human populations and to formulate hypotheses concerning their future. The genetic and anthropometric information that physical anthropologists collect provides facts about not only the groups who inhabit the globe but also the individuals who compose those groups. Practical applications of physical anthropological data include, for example, using estimates of the probabilities that children will inherit certain genes to counsel families about some medical conditions.