 3 CHAPTER whose proponents assumed that knowledge of developmental processes were superfluous to under- standing the ways and means of evolution. e split between development and evolution evident in the writings of the architects of the so- called Modern Synthesis of evolutionary biology (e.g., Dobzhansky, 1937; Mayr, 1942; Simpson, 1944) was achieved by stripping developmental processes of any meaningful role in bringing about evolutionary change. Development was described as being “programmed” in the genes (Mayr, 1988) and any evolutionarily significant changes in this program for development were thought to be com- plete at fertilization, prior to the onset of individual development (Simpson, 1967). Viewing develop- ment as the result of preformed programs encoded in the organism’s genes permitted evolutionary How individual organisms develop and how lin- eages of organisms evolve remain among the most interesting and challenging topics of investigation in contemporary biology. To anyone unfamiliar with the history of theorizing on these topics, it might seem natural to presume that knowledge of developmental processes would be necessary to understand evolutionary processes. Indeed, this supposition was widely held by biologists for much of the nineteenth century (including Charles Darwin), only to be abandoned by the dominant school of evolutionary theory (the “modern” or “neo-Darwinian” synthesis) in the twentieth cen- tury. Attempts to integrate Darwin’s theory of evo- lution by natural selection with Mendel’s theory of genetics during the first half of the twentieth cen- tury gave rise to the science of population genetics, Rethinking Epigenesis and Evolution in Light of Developmental Science Robert Lickliter and Hunter Honeycutt Abstract The dynamic and contingent nature of development revealed by work in developmental biology, neuroscience, and developmental psychology has challenged the notion of genes as the primary cause of development and renewed interest in the nature of the relations between developmental and evolutionary processes. To situate this shift in thinking currently underway across the life sciences, this chapter provides an overview of the ideas used to explain the connection between development and evolution over the last several centuries. It critiques several of these enduring ideas in light of recent findings from developmental and evolutionary science, particularly the notions that instructions for building organisms reside in their genes, that genes are the exclusive vehicles by which these instructions are transmitted from one generation to the next, and that there is no meaningful feedback from the environment to the genes. Keywords: genes, development, developmental processes, evolutionary processes, environment 04-Msblumberg-Chap03.indd 30 04-Msblumberg-Chap03.indd 30 5/20/2009 5:13:38 PM 5/20/2009 5:13:38 PM OUP  UNCORRECTED PROOF