The Shape of Life Genes, Development, and the Evolution of Animal Form
by Rudolf A. Raff
University of Chicago Press, 1996
Cloth: 978-0-226-70265-0 | Paper: 978-0-226-70266-7 | Electronic: 978-0-226-25657-3
DOI: 10.7208/chicago/9780226256573.001.0001


Rudolf Raff is recognized as a pioneer in evolutionary developmental biology. In their 1983 book, Embryos, Genes, and Evolution, Raff and co-author Thomas Kaufman proposed a synthesis of developmental and evolutionary biology. In The Shape of Life, Raff analyzes the rise of this new experimental discipline and lays out new research questions, hypotheses, and approaches to guide its development.

Raff uses the evolution of animal body plans to exemplify the interplay between developmental mechanisms and evolutionary patterns. Animal body plans emerged half a billion years ago. Evolution within these body plans during this span of time has resulted in the tremendous diversity of living animal forms.

Raff argues for an integrated approach to the study of the intertwined roles of development and evolution involving phylogenetic, comparative, and functional biology. This new synthesis will interest not only scientists working in these areas, but also paleontologists, zoologists, morphologists, molecular biologists, and geneticists.




The worst journey in the world

Old roots and tangled branches

Recapitulation, transformation, and von Baer's laws

Haeckel: Metaphor as mechanism

The embryological strand

The conflict between heredity and development

Rate genes: An attempted synthesis

Ontogeny meets the operon

An almost meeting of the minds

A deep intellectual divide

Issues for an evolutionary developmental biology

Questions of macroevolution and body plans

Homology and body plan

The living phyla

The need for phylogeny

Phylogenetic tools

Outgroups and primitive characters

Cladograms and phylogenetic trees

Diversity and disparity

Deep time

The first animals

Precambrian life and environments

Are the Ediacaran fossils animals at all?

If not animals, what?

Bodies and behaviors on the Cambrian boundary

Small shelly fossils

Unearthing the unimaginable

More body plans, faster evolution?

Evolution and progress

A summary: The importance of the fossils

Inferring molecular phylogenies

Outlining a molecular phylogeny of the phyla

The base of the metazoan radiation

The base of the radiation of the Bilateria

Strange territory: The pseudocoelomates

Coelomate protostomes


Arthropod monophyly versus polyphyly

Arthropod molecular phylogenies

The disparity of Cambrian arthropods


Molecular biology and the metazoan radiation

The Crystal Palace dinosaurs

Interpreting lost body plans

The Neanderthal's missing voice and DNA's forgotten bases

Can our methods recover phylogenies from genes?

Gene trees versus species trees

Setting the molecular "clock"

Extinct lineages affect molecular phylogenies

Fossil genes

Summing up: Phylogeny and the evolution of development

Body plans and developmental biology

Why have no new phyla appeared since the Cambrian?

Mass extinctions and big opportunities

Invasion of the land

Hypotheses on the stability of body plans

Patterns of development in the metazoan radiation

Hox genes and body plans

Evolutionary stability of early development

Radical evolutionary changes in early development

Body plans and how they develop

Fiddling with the rules

Stability of phylotypic stages

Evolution after the phylotypic stage

The developmental hourglass

The evolutionary significance of early development

Dichotomies and model systems

The limits of model systems

Rules for evolutionary developmental biology

Life history and developmental strategies

Conservation and change in early development

Developmental modes in sea urchins

Radically reorganizing development

Changes in morphogenesis

Similar genes, different embryos

Parallel and divergent mechanisms


A molluscan diversion

Evolution of development in primitive chordates: Ascidians

Vertebrate life histories and embryos: Frogs and salamanders

How general are evolutionary changes in early development?

Experimental evolution: Manipulating egg size

Regulation: The underlying flexibility of development

What price immortality?

Defining heterochronies

Local versus global heterochronies

Heterochronies need not be limited to late development

Development of the dead

The meaning of paedomorphosis

The meaning of peramorphosis

Pre-displacement and post-displacement

Genetics of heterochrony

Time and growth control

Heterochrony as a result, not a process

Human evolution

To recapitulate

The divine watchmaker


Why are there no centaurs or six-legged greyhounds?

Is selection adequate?

Whence constraints?

On the other hand

Genomic constraints

Constraint by number of cell types

Frozen controls?

Constraints imposed by the limits of structure

Constraint by complexity

Allometry: Done in by big antlers?

Mosaic bodies

Evolutionary mechanisms

Principles of evolvability


The genetic organization of modules

Standard parts

Connectivity to other modules

Temporal transformations


Duplication and divergence


A co-option event at morphological and gene levels

Limb buds: Evolution of a module

Identities of molecules signaling between limb bud modules

Genes and the execution of pattern

Commonalities in limb development across phyla

Limbs as serial homologues

Why not eight toes?

Modules set up by gene switches

Summing up

A termite history of the world

Sex and "polymorphic technology"

Fluidity of sex determination mechanisms

Evolution of eyes

Co-option of eye structures and genes

Dollo's law

Turning back the clock: Evolutionary reversals

Consequences of fluid genomes

Patagonian thinkers

Whales and the return to the sea

Wings and the insect body plan

Genes for legs and wings

Differentiating the flies from the butterflies

The echinoderm radial body plan

Rates and fossils

Exploring body plan evolution

Genes, homology, and evolution