Genetic Determinism

Genetic determinism is the belief that genes, along with environmental conditions, determine morphological and behavioral phenotypes. The term is sometimes mistakenly applied to the unscientific belief that genes determine, to the exclusion of environmental influence, how an organism turns out. As CH Waddington wrote in 1957, "It is of course a truism which has long been recognised that the development of any individual is affected both by the hereditary determinants which come into the fertilised egg from the two parents and also by the nature of the environment in which the development takes place." A related error is that geneticists and molecular biologists have only recently come to the realization that environment is essential in the development of the organism from egg to adult. In fact theorists and researchers long ago understood that genetic effects cannot be studied in isolation of the environment and that all measurements of such effects are only relative to stable external conditions. Also known since at least the 1950s is the means by which the environment influences embryonic and juvenile development, namely the epigenetic control of gene activation and deactivation.