Linkage equilibrium and disequilibrium in human population studies

It is suggested that in such genetic systems as HLA, characterized by sets of alleles at several closely linked loci, the existence of a state of linkage disequilibrium in a population indicates that this population is the result of recent hybridization between two or more populations, which may previously each have been in a state of equilibrium. Disequilibrium may, however, be modified by natural selection and by genetic drift. Examples of disequilibrium in the Rh, MNSs and HLA systems are discussed.