IMPLICATIONS OF GENETIC-VARIATION WITHIN AND BETWEEN HUMAN-POPULATIONS

Human variation is extensive both within and between populations. This variation affects all traits, including the susceptibility to disease and responses to the environment. For social and political reasons, w e tend to think of our species or our own national population as being divided into meaningful groups variously called by such terms as 'rac es', or 'ethnic' groups, and there is often an implicit assumption tha t these groups are relatively homogeneous within and very different be tween. Examples are given to show that there are major differences in the frequency of genetic susceptibility to various diseases between so me such groups, but that the amount of variation among individuals is extensive even within such groups. Population subdivision can be usefu l for studying disease, but human variation is a general phenomenon ti ed to groups via their population and geographic history, not value-ba sed categorical differences.