Overview

The extent to which genes differ between individuals, races, and species has been the central theme of population genetics in the twentieth century. New experimental methods developed in the 1960s allowed the first estimates of the degree of genetic variation in natural populations of human and non-human species. The unexpected finding was that on average, at least one out of every three genes in a species had more than one molecular form, revealing substantial genetic variation among members of the same species. In humans related studies revealed that the genetic variation between individuals of the same race was much more pronounced than that between races. These findings called for a re-thinking of the role of natural selection in evolution and brought a deeper understanding of the close symbiosis between genes and the environment. The inadequacy...