Discarding the concept of race as misleading, this text examines the biological basis for human variation and biological diversity at the population level. This is appropriate because of the many ways in which humans can adapt to environments, organize activities, and regulate breeding behaviour. The biological diversity of the human species is a reflection of these adaptations. This text reviews the history, behaviour, demographic structure of contemporary populations, their effects on the distribution of major genetic polymorphisms, and distinctions of body form, size and skin colour.