ADAPTATION, SELECTION, AND PLASTICITY IN ONGOING HUMAN EVOLUTION

An examination of some aspects of the nature of human genetic org as revealed by the phenotypes (human beings) which express it, assuming that 'a genetic org which can produce phenotypes capable of such a wide range of activities as those performed by humans must have certain rather unusual qualities.' It is argued that plasticity has operated & will continue to operate 'to maintain the genetic unity of the human species.' However, since plasticity leads to a better adjustment, 'it may be expected to render adaptation less necessary, & therefore to slow down the rate of evolution in the direction of genetic specialization. At the same time mutations leading to a greater degree of plasticity are likely to be selected; for, if our environment remains as changeable & diverse as it now is, this may be essential.' I. Taviss.