Evolutionary Epigenetics

Abstract

Abstract Until recently, the Modern Synthesis of evolution forged in the 1930s and 1940s was the almost unquestioned basis of evolutionary thinking. At its core were two assumptions about variation. The first was that inherited differences between individuals are the result of genetic differences. The second was that the generation of new genetic variation is blind to function: variations do not arise as adaptive responses to environmental conditions. Ernst Mayr, one of the founders of the Synthesis, insisted repeatedly that inheritance is not “soft”-the hereditary material cannot be modified by environmental influences on the body, nor can it be changed by the use and disuse of body-parts (e.g., see Mayr 1982, p. 552). Lamarckism was totally rejected. Molecular genetics at first hardened the assumption that the only variation that is relevant for evolutionary change is genetic variation. Evolution was seen in terms of changes in DNA, with new variants arising through chance alterations in DNA sequences. However, developments that began in the mid-1970s have led some evolutionary biologists to question the adequacy of this view of hereditary variation. They recognize that heredity involves more than genes and DNA. Studies of human and animal cultures have shown that variations can be transmitted behaviorally and culturally, and cell biologists have shown that genetically identical cells can transmit different structural and functional properties to their descendants. In other words, sometimes variations in phenotypes, as well as genotypes, are inherited. Moreover, since the generation of both cellular and cultural phenotypes is strongly.