The more significant developments in the field of human population genetics during the past decade can for the most part be subsumed under three headings, as follows:1. The recognition of an increasing number of genetic traits capable of serving as analytic tools in population studies.2. The recognition that many of these traits attain frequencies, although some only in limited areas, such that they have to be labelled genetic polymorphisms. Table 1 is an attempt to list the presently recognized human polymorphisms for which the genetic basis seems clear.3. The emergence of at least a few clues as to the factors responsible for the maintenance of some of the plymorphisms, although it must be confessed that for the majority of the traits listed in Table 1, there is as yet no real insight into their role in populations.As is well known from the contributions of Fisher, Wright, Dobzhansky, Lerner, Crow, Kimura, and others, genetic polymorphisms have the property of acting as stabilizing mechanisms in maintaining certain aspects of the fitness of populations. Consequently, whereas what we may term the “classical model” of the dynamics of a genetic locus in a population looked to mutation pressure as the source of the impairment of population fitness which could be traced to that locus, the “polymorphic model” views that impairment as in part a price a population pays for the maintenance of an optimum level of heterozygosity at that locus. The two models have such profoundly different practical and philosophical consequences that it is small wonder that in recent years the running discussion of their relative merits and roles has generated a degree of heat matched by few other current biological questions.
Acknowledgement to Reviewers of Human Population Genetics and Genomics
