Neophenogenesis: a developmental theory of phenotypic evolution.

An important task for evolutionary biology is to explain how phenotypes change over evolutionary time. Neo-Darwinian theory explains phenotypic change as the outcome of genetic change brought about by natural selection. In the neo-Darwinian account, genetic change is primary; phenotypic change is a secondary outcome that is often given no explicit consideration at all. In this article, we introduce the concept of neophenogenesis: a persistent, transgenerational change in phenotypes over evolutionary time. A theory of neophenogenesis must encompass all sources of such phenotypic change, not just genetic ones. Both genetic and extra-genetic contributions to neophenogenesis have their effect through the mechanisms of development, and developmental considerations, particularly a rejection of the commonly held distinction between inherited and acquired traits, occupy a central place in neophenogenetic theory. New phenotypes arise because of a change in the patterns of organism-environment interaction that produce development in members of a population. So long as these new patterns of developmental interaction persist, the new phenotype(s) will also persist. Although the developmental mechanisms that produce the novel phenotype may change, as in the process known as "genetic assimilation", such changes are not necessary in order for neophenogenesis to occur, because neophenogenetic theory is a theory of phenotypic, not genetic, change.