SUBJECT: Book Review - The Dynamics of Evolution
The Dynamics of Evolution -
The Punctuated Equilibrium Debate in the Natural and Social Sciences
(Eds) Albert Somit & Steven A. Peterson
Cornell University Press 1992
[ evolutionary biology, anthropology, politics ]
The punctuated equilibrium debate is one of the few controversies within
evolutionary biology that have come to popular notice. No doubt this is
largely a result of the popular writings and high profile of Stephen Jay
Gould, the theory's leading proponent. _The Dynamics of Evolution_,
coming twenty years after the paper by Gould and Eldredge that
originally sparked the debate, is a retrospective evaluation of the
theory and the surrounding debate, pitched at a level that makes it
approachable by anyone with a general background in evolutionary
biology. (Perhaps someone who has read the popular writings on evolution
of Dawkins and Gould and wants to know what the status of the debate
is.) Some of the first six essays in this book (on the biological theory
of punctuated equilibrium) will themselves be important works in the
ongoing debate; as well as these _The Dynamics of Evolution_ contains
another six essays on implications for the social sciences (the editors
themselves are political scientists rather than biologists).
Punctuated equilibrium is the idea that "most" evolutionary change
happens in geologically "brief" speciation events separated by long
periods of "stasis". As the essays in this book demonstrate there is a
great deal of uncertainty about what exactly this means and whether it
is true or not (hence my scare quotes).
The opening essay by Ernst Mayr is a broad attempt to explain what the
theory of punctuated equilibrium is and what the debate has been about.
Mayr describes the different things that have been labelled "punctuated
equilibrium", with a concern to clarify some points of uncertainty. His
view is generally very favourable; apart from some of the more extreme
ideas regarding saltationism (production of new species by large single
mutations) which he sees Gould as having toyed with for a few years, he
believes that most of the claims associated with punctuated equilibrium
are in fact either true or in the process of being tested, and that the
issues involved are significant. However he stresses that punctuated
equilibrium does not "transcend" Darwinism in any way, and is in fact
solidly in the Darwinian tradition.
In the second essay we have a discussion of punctuated equilibrium
"straight from the horses mouth"; Stephen Jay Gould himself explains the
origins of punctuated equilibrium, answers some of its detractors'
arguments, and considers some of its wider implications. As the editors
say in the introduction, so closely is Gould associated with punctated
equilibrium that this is almost an "apologia pro vita sua". His ideas
are clearly less extreme than some of the other essays in this volume
seem to think, and though he claims that there have been no major
changes in his ideas on the subject, this seems to be rather arguable.
Next up Steven Stanley presents some of the empirical evidence
supporting punctuated equilibrium. This includes evidence for effective
stasis in some lineages and evidence for extremely rapid speciation in
others. It is extremely hard to evaluate this evidence, given the
sampling problems inherent in choosing lineages to study that Stanley
himself points out, but there seems little doubt that there is evidence
for punctuated equilibrium in evolution and that further work will make
it clearer exactly how important it actually is.
An essay by Eldredge, the other founder of punctuated equilibrium, is
largely about hierarchical evolution rather than punctuated equilibrium.
He also makes a few very general comments about possible metaphorical
application in the social sciences (looking forward to the second
section of the book).
The only really dissenting voice in this discussion is that of Antoni
Hoffman. His essay is a general attack on the theory of punctuated
equilibrium; he claims that the weak form (that rates of evolutionary
change vary) is trivial and says nothing that wasn't known to Darwin,
the strong from (macromutations and saltationism) is false, and the
moderate form (widespread stasis in evolutionary lineages) is
untestable. He does admit that punctuated equilibrium has had heuristic
value in sparking debate and suggesting research. Again it is evident
that there is confusion as to whether (and how strongly) Gould actually
pushed saltationism, but it is clear that he no longer does so; hence
criticism of the "strong" version of punctuated equilibrium is now
peripheral to the main debate. Given the palaeontological evidence
presented by Stanley and Gould in this volume (and by others elsewhere),
Hoffman's claim that the moderate version is untestable seems hard to
sustain, although it is clear that testing it is more complicated than
was at first thought.
The final essay in this section is by the philosopher Michael Ruse, who
has changed his original negative opinion of punctuated equilibrium and
now considers it to have many of the characteristics of a paradigm
shift. He concentrates his attention on the work of Stephen Jay Gould,
and has some particularly interesting things to say about the
relationship between punctuated equilibrium and Gould's position on
other issues (such as his Marxism, his aversion to sociobiology, his
Jewishness, etc.). Ruse's conclusion is that the main influence on
Gould's thinking is not any of these in particular, but his general
background in European philosophy, and in particular in a biological
tradition stretching back to Goethe that stresses form rather than
The second section, titled "Implications for the Behavioural Sciences",
begins with an essay by Kenneth Boulding on "Punctuationism in Societal
Evolution". This is basically a collection of comments on broad
similarities between biological and social systems, with some reference
to "punctuationism". It is far too vague to be interesting; most of what
it says is either trivially true or so sweepingly general that truth is
rather irrelevant. A couple of the statements about biological evolution
are worded in such a way as to make me slightly queasy; it is not
entirely clear that the author understands the Central Dogma of
molecular genetics and how its existence means there are fundamental
differences between biological evolution and societal evolution.
Susan Cachel's "Punctuated Equilibrium and Evolutionary Anthropology" is
rather peripheral to punctuated equilibrium, being an attack on the
misuse of cladistic systematics in palaeoanthropology. (She thinks an
approach stressing evolutionary ecology, morphological change, etc. is
more useful than one based purely on classification and construction of
phylogenetic trees.) At any rate, though punctuated equilibrium is often
coupled with cladistic systematics, it seems to me that the two are very
uneasy bedfellows, and so her whole argument has little to do with the
punctuated equilibrium debate.
Allan Mazur looks at the evolution of human social behaviour. He argues
for a methodology based on progressive changes throughout the order
primates. (Which seems to assume some ideal of progress as well as
gradualist change.) He doesn't think there is enough evidence to decide
whether punctuated events are important in human evolution or not. On a
similar note Brian Gladue argues that the punctuated equilibrium debate
is irrelevant to psychobiology. The example he considers is
The last two essays are on links between the punctuated equilibrium
debate and politics. Glendon Schubert looks at parallels between
catastrophism in evolution and in politics, with human effects on
biological systems (imminent ecological disaster) as a link.
Roger Masters looks at links between biological and political theories
in the history of philosophy. He looks at Aristotle, Empedocles and
Lucretius, and at Hobbes, Rousseau and Marx. His conclusion is that,
since amongst them they hold all possible combinations of views on
gradualism/punctuationism, it seems unlikely that either scientific
position can be invalidated because of its proponents political beliefs.
However I remain entirely unconvinced that even a perfect correlation
between gradualist (or punctuationist) political beliefs and the
corresponding evolutionary ideas would in fact have any consequences for
biological theory, which is what Masters seems to be saying.
In general I was a bit disappointed by the essays in the second section.
I would have liked to have seen something on parallels between species
and cultures (the controversy over whether species are "real" entities
in evolutionary theory is arguably considerably better formulated than
arguments about the reality of cultures in anthropology), and between
evolution and cultural change, perhaps from an anthropological
viewpoint. It seems to me that a punctuated model of human evolution
could have important consequences; even if there is not enough data to
say anything definite a bit of wild theorising wouldn't have gone amiss.
(For example, is the "aquatic ape" theory compatible with punctuated
speciation of homo sapiens?)
Some of the essays in _The Dynamics of Evolution_ were a bit
disappointing, but they are all interesting and some of them are likely
to be extremely important. Anyone interested in the punctuated
equilibrium debate will want to read this book.
Danny Yee (email@example.com)