Inherency

Abstract

Inherency in development and evolution is the idea that aspects of the phenotype are latent in the organism’s material identity and that these features will spontaneously emerge if the conditions are right. This chapter is primarily concerned with inherency of form in the animals (metazoans). Regarding development, inherency means that certain structural motifs (e.g., tissue layers, lumens, segments, appendages) can be readily generated by physical organizing forces acting on tissue masses, with minimal programming by the genome. With respect to evolution, it means that body plans and organ forms will inescapably be characterized by these motifs despite their not having arisen by multiple cycles of selection for improved fitness. The notion of inherency is therefore at odds with the theory of natural selection and its twentieth-century embodiment, the modern evolutionary synthesis. While a recently proposed extended synthesis relaxes the gradualism, gene-centrism, and assumption of unbiased modes of variation of the modern synthesis, it is similarly challenged by inherency, since in most renditions it remains focused on adaptation as the criterion of evolutionary success. Inherency makes generation of form ontologically prior to its uses. It implies that since organisms are limited with respect to potential morphologies, and innovation within these limits may be sudden and unprecedented, the major factor in establishment of new lineages is not competitive struggle in preexisting niches but ingenuity of organisms in using the means at their disposal.