Heterochrony

by

Miriam Zelditch

• LAST REVIEWED: 24 March 2021
• LAST MODIFIED: 25 April 2022
• 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, but both the meaning of the word and the evolutionary significance of heterochrony have changed more than once since the word was first introduced in Haeckel’s Naturliche Schopfungsgeschichte (Berlin: Georg Reime, 1868). Gould’s Ontogeny and Phylogeny (Cambridge, MA: Belknap Press of Harvard University Press) is the foundational work that reinvigorated the study of heterochrony; the first half of that book is a historical overview of the subject; the second half is about the significance of heterochrony (and of development) for evolution. Heterochrony has been a major focus of evolutionary developmental biology, but the definition of the term and its biological significance have repeatedly changed. There are at least four distinct concepts of heterochrony, two of which are nearly mutually exclusive, and the others partially overlap both. Since the 2010s, that conceptual incoherence has decreased, but heterochrony remains a complex concept because of the disparate views about what it means as a word, and what follows from that: the biological significance of heterochrony and the methods for detecting it empirically. The concept remains a focus of evolutionary developmental biology because the core of ideas central to most concepts of heterochrony are now central to the field: 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 or rate. That concept links heterochrony to theories about developmental integration and modularity and thus to theories of intrinsic constraints. 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 views of heterochrony. Haeckel 1868 is the work that introduced the concept; Gould 1977, McKinney and McNamara 1991, Raff and Wray 1989, and Smith 2001 present overviews of what heterochrony is, how it can be studied, and what it means for evolutionary biology. Li and Johnston 2010 (cited under Heterochrony as the Evolution of Development) 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 Press of Harvard University Press.

  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.

• Haeckel, E. 1868. Naturliche Schopfungsgeschichte: Gemeinverstandliche wissenschaftliche Vortrage uber die Entwickelungslehre im allgemeinen und diejenige von Darwin, Lamarck und Goethe. Berlin: Georg Reime.

  The book that introduced the concept of heterochrony and discussed its evolutionary significance in context of the theory that evolutionary change occurs by recapituation, “ontogeny recapitulates phylogeny” and the exceptions to that rule, that is, heterochrony.

• 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.

  DOI: 10.7208/chicago/9780226256573.001.0001

  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.