Heterochronic Variation and Environmental Selection
Classically, heterochrony has been mainly concerned with evolutionary change at the species level. It has been viewed as little more than an ancillary part of evolutionary theory that deals largely with patterns of morphogenesis. But as discussed in Chapter 3, in our view heterochrony is a fundamental process of morphogenesis. Biological evolution, after all, arises from the complex interplay between extrinsic factors, such as natural selection, and intrinsic factors, such as the nature of an organism’s developmental system. This has been shown to embrace two fundamental concepts (Gould, 1989): historicism, that is, form as dictated by past events and past relationships: and formalism, interpreted as the “rules of structure,” wherein an organism’s properties are constrained to some degree by the physical consequences of its inherent structure.
KeywordsSexual Dimorphism Phenotypic Plasticity Juvenile Hormone Developmental Program Extrinsic Factor
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