ABSTRACT
Mutation and recombination increase human diversity by generating new alleles and new haplotypes respectively. Genetic drift reduces diversity, and results from the random sampling of one generation from the preceding one, causing random change in allele frequencies. The weakness of Hardy–Weinberg equilibrium as a test for events that alter allele frequency empha-sizes the importance of more sophisticated population genetic models. Assortative mating augments genetic drift by decreasing the effective population size, whereas the opposite is true for disassortative mating. Unlike genetic drift, mutation, and selection, migration cannot change spe-cieswide allele frequencies, but it is capable of changing allele frequencies in populations. The vast majority of polymorphisms observed in populations are transient, awaiting eventual fixation or elimination by genetic drift. Some human populations exhibit high incidences of multiple genetic diseases that are rare in surrounding populations.
