Genetic Variation and Cultural Evolution

Abstract

The breakdown of isolation between groups is theoretically expected to increase the amount of variation within groups. One measure of the in-group variation is the frequency of heterozygosity; this should increase in accordance with the evolution of culture. Concurrently, the variation between groups should diminish. A survey of mean AB, MN, and Cc heterozygosity is undertaken on 252 ethnic groups. Each is classified by level of socio-cultural integration: band, tribe, chiefdom, and state. The geographical distribution of the variables is mapped. Individual ethnic groups are organized into thirteen regions (heterographic areas) which provide reasonably independent tests of the hypothesis in question. Mean blood group heterozygosity for the three loci investigated is 32.47%±0.59 among states as compared to 24.86%±0.49 among primitive societies. The difference (7.61%) is highly significant. Furthermore, in-group heterozygosity increases with each stage of social evolution. The variance between groups diminishes consecutively. It is concluded that the distribution of heterozygosity is strongly dependent upon cultural evolution. Primitive societies are genetically more homogeneous. Empiric evidence supports the Law of Biocultural Evolution. Multiple factor traits would be expected to show an analogous pattern. In contrast to man in general, human paleontologists should find primitive societies to provide closer models of the in-group and between-group variance of fossil hominids. The role of biocultural evolution toward maintaining and increasing human variation is discussed.