A Few Words About Evolution
by David B. Wake
e live
in a darwinian world. For many evolutionary biologists the ever-extending
grand evolutionary synthesis promulgated in the 1930s and 1940s offers
adequate explanations and serves as a consistent generator of testable
hypotheses. For Stephen Jay Gould it is but a foundation, wholly inadequate
to be a framework within which to build. Evolution proceeds in a
hierarchical manner, so proper analysis requires a hierarchical approach,
Gould believes.
Modern darwinians, being largely reductionist in
approach—while paying some lip-service to the possibility of
constraints, the reality of mass extinctions and the like—view
evolution in general as microevolution plus lots of time and some
contingency. Gould strongly rejects this perspective. His views are well
known, but they have had surprisingly little effect on some of the core
disciplines in evolutionary biology, such as population, and quantitative
and evolutionary genetics, whose practitioners see themselves as defenders
and extenders of the darwinian message. In The Structure of Evolutionary
Theory Gould makes a direct, intellectually rigorous argument that a
hierarchical perspective would not only enrich modern darwinism, but that
it is essential. This book is a manifesto for a new kind of evolutionary
biology, one that makes full use of many kinds of knowledge as well as
diverse 'ways of seeing'.
This large book demands attentive reading. Gould uses
many more words than most writers and the book appears not to have been
edited at all. Those who enjoy Gould's erudition and style will find this
to be a stimulating and illuminating book; it will infuriate others. There
are intellectual wars in progress in the evolutionary-biology community,
but most researchers seem to care little about battles engaged around issues
such as hierarchical versus reductionist approaches, and structuralist
versus functionalist versus historical perspectives. I believe that these
are important issues, and that in the long run evolutionary biology will
have to confront them. Gould's book, an intellectual tour de force and a
work of serious scholarship, will be a permanent factor in the struggle to
understand how life has evolved.
Gould knows the book is long and daunting and has
supplied readers with a kind of abstract, itself 89 pages long. In this
opening chapter he previews, but cannot really encapsulate, the many deeply
analytical historical and philosophical treatments to come. This is a long
and circuitous argument that new knowledge and new macroevolutionary
explanations have been so substantial that a full exposition of evolutionary
theory within the domain of darwinian logic "must be construed as basically
different from the canonical theory of natural selection, rather than simply
extended". This point is made repeatedly throughout the book, lest anyone
miss it.
The strategy is to examine the historical roots of
evolutionary theory in great detail and to show how earlier workers, even
Darwin (but excluding Wallace, who remained the ultimate pan-selectionist),
were forced to resort to hierarchical thinking at some point in their
intellectual journeys. The book is a veritable history of evolutionary
biology, but not all of it, of course. Gould sets the agenda and discusses
what he wishes from his point of view: that of a strong advocate for an
expanded and greatly modified evolutionary theory.
All Gould's familiar arguments are here, with emphasis
on levels of selection, punctuated
equilibrium, and their contribution to the development of Gould's
hierarchical perspective. His points are forcefully made, but the arguments
of only some of his detractors are considered. Gould makes a convincing
case for the "hardening"
of the adaptationist perspective during, and especially at the end of, the
grand evolutionary synthesis in the middle of the twentieth century. He
charges that evolutionists became almost blindly channelled. Selectionists
will complain that their position is oversimplified.
In a time when we are in something of an intellectual
revolution in our understanding of species and species formation, Gould is
unrelentingly stubborn in his insistence that speciation is a big deal, that
species are individuals, and that species selection is the critical keystone
of a hierarchical approach. Close study of species formation has made me
question the reality of species as bounded entities, and I am wary of the
perspective that species are individuals. I find clade selection an
attractive and more general alternative to species selection, but Gould will
not give ground. Many of us are attracted to aspects of punctuated
equilibrium, and the concept has stimulated much research over the past 30
years. But the insistence that it is a theory of the deployment of species
over time and space makes many uneasy and leads to doubts that it is the
core concept for the new hierarchical theory of evolution.
I thoroughly enjoyed many parts of the book, for example
the long and rewarding chapter on the evolution of development with its
strong focus on the positive evolutionary effects of constraints, and the
concluding chapter that deals extensively with spandrels. The structuralist
message of these chapters is strong and clear, but it is integrated with
functionalist and historical perspectives as well. Parallel evolution is
given the attention I believe it merits, and Gould does an admirable job of
showing why it is important. A fan of Hox genes (he loves the word
'hoxology'), Gould also shows the importance of developmental genetics for
his hierarchical perspective and for understanding the evolution of form in
organisms.
Gould, the most widely known evolutionist of our time,
has remained active in research while at the same time communicating his
evolutionary message to the public through his prolific writings and
appearances. This book demonstrates that he is not just a popularizer, but a
major intellectual force in his discipline. Yet one can predict a strong
negative reaction because the book is annoyingly self-congratulatory and
self-serving. But what can he do? He is certain that he is right! A
strength, and at the same time a weakness, of this book is that the author's
powerful personality emerges on nearly every page. The important messages of
this book are appreciated most fully when the reader accepts and enjoys the
idiosyncrasies of this extraordinary man.
[ David B. Wake, "A few words about evolution,"
Nature,
416 (April 25, 2002): 787-788. ]
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