Heterochrony

by

Miriam Zelditch

• LAST MODIFIED: 28 February 2017
• DOI: 10.1093/obo/9780199941728-0087

Introduction

Heterochrony, broadly defined, refers to evolutionary change in the rate or timing of development. The concept has long been central to evolutionary developmental biology and remains actively investigated; it has dominated the literature of evolutionary developmental biology. What makes the literature complex is that there are at least four distinct concepts of heterochrony, two of which are nearly mutually exclusive, and the others partially overlap both. Taken as a whole, the literature is conceptually incoherent, and the mathematical formulations of heterochrony are incommensurate. Not surprisingly, it is difficult to generalize about the causes, consequences, or evolutionary significance of heterochrony. Nevertheless, one complex of ideas is central to most concepts of heterochrony: the related concepts of “dissociability,” “modularity,” and “integration,” on which definitions (and theories) of heterochrony are grounded. Dissociability is the ability to alter individual developmental processes or stages independently of others, and it is dissociability that allows for shifts in (relative) developmental timing. It is just that the term “heterochrony” has different relationships to dissociability and modularity and integration, because “heterochrony” is variously a consequence of a highly integrated or modular developmental system. Despite the confusing semantics of “heterochrony,” the concept remains central for studies of developmental integration and modularity, as well as for theories that examine the evolution of dynamic form and function. The major objective of this article is to clarify the conceptual frameworks associated with each definition of heterochrony and to highlight major themes in the literature, keeping semantic issues to a minimum.

General Overviews

There are no comprehensive overviews of heterochrony, but there are overviews of particular view of heterochrony. Gould 1977, McKinney and McNamara 1991, Raff and Wray 1989, and Smith 2001 all are overviews of what heterochrony is, how it can be studied, and what it means for evolutionary biology. Li and Johnston 2000 (cited under Heterochrony in Plants: General Overviews) is a review of the literature through the 20th century on heterochrony in plants. Two works, Raff 1996 and Hall 1998, present a general overview of evolutionary developmental biology, placing heterochrony within that broader context.

• Gould, S. J. 1977. Ontogeny and phylogeny. Cambridge, MA: Belknap.

  The book is responsible for the renaissance of interest in heterochrony. The first half is a history of the concept, and the second is an argument for the importance of the parallelism between ontogeny and phylogeny.

• Hall, B. K. 1998. Evolutionary developmental biology. 2d ed. London: Chapman & Hall.

  A scholarly introduction to evolutionary developmental biology. Part 7 is on “Patterns and Processes, Time and Place,” and chapter 24 in that section is “Time and Place in Evolution: Heterochrony and Heterotopy.”

• McKinney, M. L., and K. J. McNamara. 1991. Heterochrony: The evolution of ontogeny. New York: Plenum.

  DOI: 10.1007/978-1-4757-0773-1

  The title of the book summarizes its major argument: nearly all evolutionary change is due to heterochrony, broadly defined as an evolutionary change in rate or timing.

• Raff, R. A. 1996. The shape of life: Genes, development, and the evolution of animal form. Chicago: Univ. of Chicago Press.

  A highly readable overview of evolutionary developmental biology for a broad audience. Chapter 1 conveys the influence of the biogenetic law on scientists who risked (and lost) their lives to find the embryos that would reveal phylogeny; chapter 8 is titled “It’s Not All Heterochrony.”

• Raff, R. A., and G. A. Wray. 1989. Heterochrony: Developmental mechanisms and evolutionary results. Journal of Evolutionary Biology 2.6: 409–434.

  DOI: 10.1046/j.1420-9101.1989.2060409.x

  Broadens the concept of heterochrony, extending it to processes. Places that expanded concept in the context of theories of dissociability and articulates the spatial, temporal, and organizational domains of heterochrony. Essential reading for understanding how the concept (as defined by Stephen Jay Gould) evolved and what is meant by “process” and “pattern” heterochrony.

• Smith, K. K. 2001. Heterochrony revisited: The evolution of developmental sequences. Biological Journal of the Linnean Society 73.2: 169–186.

  DOI: 10.1111/j.1095-8312.2001.tb01355.x

  Argues for broadening the concept of heterochrony to encompass what it had traditionally meant before being narrowed by Gould. Contains an introduction to sequence heterochrony, emphasizing the value of the approach and a summary of several studies that use this approach.