a history of genetics?
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TRENDS in Genetics Vol.18 No.5 May 2002
http://tig.trends.com
272 Forum
A foot in each world
Captivating Life: A Naturalist in the
Age of Genetics
by John C. Avise Smithsonian Institution Press, 2002. $24.95 hbk (222 pages) ISBN 1 56098 957 2
Throughout the history of biology, there has
been an uneasy coexistence between two
very different traditions – a field-orientated
one with its emphasis on natural history, and
a laboratory-based one with its emphasis on
experimentation. Tensions between these
two traditions intensified after the discovery
of the structure of DNA spurred the rise of
molecular genetics. In his autobiography
[1], Edward O. Wilson documented
these ‘molecular wars’as they affected
Harvard’s biology department during the
1950s. Although molecular wars continue
to rage, or at least smolder, in most biology
departments, a new synthesis has emerged
in recent decades. With increasing frequency,
molecular genetic techniques are being
used to address ecological and evolutionary
questions, leading to the creation of new
fields such as molecular ecology and
phylogeography. John Avise, who has been
at the forefront of the creation of these
fields, discusses their maturation and his
own in his autobiography, Captivating Life.
Avise’s first passion was natural history.
Growing up in Michigan, he developed a
particular fondness for birds and fossils.
During summers as a teenager, Avise
assisted Harry Pederson filming undersea
life in the Bahamas. Here, Avise learned
the ‘concept of observational natural
history in its own right, in which novel
secrets of science might be learned with
suitable diligence’. Avise’s maturation as a
natural historian was also substantially
influenced by his reaction to the Vietnam
War. He shares an illuminating excerpt
from the 1970 letter he wrote as part of his
application for Conscientious Objector
status wherein he explains his philosophy
about environmentalism and the war .
Avise was impressed by the power of
genetic tools as a graduate student. Under
the tutelage of Robert Selander, then at
the University of Texas, Austin, Avise
used the then-new technique of allozyme
electrophoresis to examine the genetic
variability of cave- and surface-dwelling
populations of fish in the genus Astyanax. In
less than a year, he collected sufficient data
for a Master’s thesis that was quickly turned
into a classic paper [2]. Among other things,
Avise found that surface populations have
markedly greater genetic diversity than do
cave populations. For his doctorate, Avise
joined Francisco Ayala’s lab at the University
of California, Davis, and examined patterns
of genetic diversity among species of
minnows and sunfish. Although there are
many more species of minnow than of
sunfish, species within each group showed
comparable levels of divergence. This
pattern was interesting in that it was
consistent with phyletic gradualism, the
claim that morphological change generally
occurs gradually and within lineages. The
pattern was seemingly inconsistent with the
competing claim of punctuated equilibrium,
which states that morphological change
occurs in fits and starts and generally
coincides with the splitting of species.
Although working with very diverse
taxa, Avise’s research program has been
unifying. Not only did he bridge the gap
between the lab and the field, Avise
also helped to bridge the gap between
population genetics and phylogenetics by
focusing on phylogenies below the species
level. Avise was one of the driving forces in
investigating how geographical features
influence phylogenetic clustering. He also
attempted to forge a consilience between
the seemingly antithetical biological
species concept (which emphasized
reproductive isolating barriers) and the
phylogenetic species concept (which
emphasized diagnosably distinct character
states) [3]. Perhaps the diversity of taxa
and questions he has worked on helped
Avise to see the conceptual unifications.
Captivating Life provides a rare
glimpse into the thoughts of an active
researcher in mid-career. Avise not only
discusses issues related to science, but
also those of lab management and
graduate student training. For instance,
Avise strongly disagrees with the
conclusion by the National Research
Council (NRC) that the US grants too
many PhD degrees ‘relative to its needs’
in the biomedical sciences. Instead, he
believes that the current and looming
environmental crises and the
technological breakthroughs in genetic
engineering require the training of many
more biologists in both genetics and
environmental biology. Although my
personal opinion is closer to that of the
NRC, Avise’s defense of his position is well
considered and worth reading.
Science, as Avise concisely and accurately
describes, is ‘…a principled manner by which
phenomena are explored. The epistemological
hallmarks of science are objectivity, critical
open-mindedness and the ruthless evaluation
of alternative hypotheses against evidence’.
Avise’s autobiography also shows that the
science of life, from natural history to
molecular genetics, can be captivating.
Norman A. Johnson
Dept of Entomology, University ofMassachusetts, 102 Fernald Hall, Amherst,MA 01003, USA.e-mail: njohnson@ent.umass.edu
References
1 Wilson, E.O. (1994) Naturalist, Island Press
2 Avise, J.C. and Selander, R.K. (1972)
Evolutionary genetics of cave-dwelling fishes of
the genus Astyanax. Evolution 26, 1–19
3 Avise, J.C. and Wollenberg, K. (1997)
Phylogenetics and the origin of species. Proc.
Natl. Acad. Sci. U. S. A. 94, 7748–7755
A history of genetics?
Gene Action: A Historical Account
by Werner Maas Oxford University Press, 2001. £22.50 hbk (176 pages) ISBN 0 19 514131 8
I had always assumed that Werner Mass
was a biochemist by training who had
exploited genetics in his studies of
biosynthesis and its regulation in bacteria.
From this book, however, I learnt that he
was initially a geneticist and viewed his
work as biochemical genetics; he was not,
as I had thought, only a user of mutants.
Gene Action is a historical account of
genetics, and it begins with Mendel rather
than with Miescher. Based on lectures Maas
has given on the history of molecular
genetics, it is an amalgam of material taken
from books and his own recollections. Many
of the founders of modern genetics have
written accounts of the past 50 years and, of
course, we have Horace Judson’s book, The
Eighth Day of Creation [1]. It is difficult to
cover such a long story, from the beginnings
of genetics to the human genome sequence
in 150 pages, and, inevitably, there are
sections where the accounts are sketchy
and, on occasion, inaccurate.
Book Review
TRENDS in Genetics Vol.18 No.5 May 2002
http://tig.trends.com
273Forum
Only the old are interested in history,
the young, as I have written elsewhere,
think only of the past two years – although,
perhaps, this now needs to be amended to
the past two weeks. One has to have gone
far down the road to be able to discover
how the roots of one’s life and work are
connected with others in time and place.
For those interested only in the new
buds, history must seem a tedious
preoccupation, and unless it is well done
and challenges the reader with perhaps a
new view or a different integration of the
past, it can become very boring. I am much
more interested in the personal slant on
past events; Stendahl’s letters describing
Napoleon’s retreat from Moscow give one
a strong feeling of participation that no
military history could accomplish. The
memoir, cast on a small scale, is much
more fascinating than the broader picture
of the past events. The book livens up
considerably when it becomes the memoir
and Maas tells us of his personal
experiences; of working with Bernie Davis
and his encounters with the great.
The best part of the book is the picture
on the front cover, showing the younger
Jacques Monod with that intense and
half-amused look those who knew him will
always remember. Even the young, who
know nothing about β-galactosidase
induction will be gripped by it.
Sydney Brenner
The Molecular Sciences Institute, Inc., 2168 Shattuck Avenue, 2nd Floor, Berkeley,CA 94704, USA.e-mail: sbrenner@molsci.com
Reference
1 Judson, H.F. (1996) The Eighth Day of Creation:
Makers of the Revolution in Biology, Cold Spring
Harbor Laboratory Press
Changing times for
heterochrony
Beyond Heterochrony
edited by Miriam Leah ZelditchWiley Liss, 2001. £74.50 hbk (392 pages)ISBN 0 471 37973 5
Despite the recent growth of ‘Evo-Devo’,
there is still a large conceptual gulf
between evolutionary and developmental
biologists. The main area of common
ground is the discovery, of a remarkable
degree of homologous mechanism in the
development of apparently disparate
creatures. Indeed, developmental
biologists are often tempted to think
that there are not really any significant
differences between Caenorhabditis
elegans, Drosophila and the mouse! Those
developmental biologists who take a
particular interest in evolutionary change
tend to try to identify individual items of
the genetic program that have been altered
to bring about particular morphological
alterations in closely related organisms.
The approach of evolutionary biologists
has been totally different. Mesmerized by
Stephen J. Gould’s book Ontogeny and
Phylogeny [1], they seem to be convinced
that just one process, called heterochrony,
underlies most morphological change. There
are various definitions of heterochrony, but
in general it means an alteration in timing
of some aspect of development. The classic
examples of heterochrony are well known;
for instance, the phenomenon of neoteny
(more strictly ‘paedomorphosis’) whereby, in
certain salamanders (including the axolotl),
sexual maturity occurs in what is usually
considered the larval stage.
Beyond Heterochrony is a thoughtful
collection that addresses the current
status of the concept and its utility in
evolutionary studies. An important theme
is the application of sophisticated new
morphometric methods, to determine
whether heterochrony has actually happened
in particular evolutionary changes. For
example, a chapter by Nehm on two extinct
species of margenellid gastropods shows
that their relationship can be interpreted
as heterochronic. By contrast, several
chapters, for example those by Webster
et al. on trilobites and by Zelditch et al. on
modern pirhanas, shows that relationships
can be more complex, and some, such as
Shapiro and Carl’s chapter on skink limbs,
seem to rule out heterochrony as a factor.
Another theme in the book is the
resurrection of the concept of ‘heterotopia’
as an alternative to heterochrony.
‘Heterotopia’means a change in the
position of a structure, and relates more
directly to modern developmental biology
than does heterochrony, because of
the high level of understanding of the
molecular basis of spatial patterning
that now exists. Several of the chapters in
this book conclude that there has been a
degree of heterotopia in their objects of
study; for example, Frolich’s chapter on
the origin of flowers and Roopnarine’s
chapter on species of the bivalve Chione.
It seems to me that there are two general
problems with the obsession of evolutionary
biologists with heterochrony. First,
elaboration of the concept has tended
to broaden its meaning until it conveys
nothing but a vague idea that a change
is rooted in some aspect of development.
The way this can occur is illustrated by
considering the definition of Raff, to whom
heterochrony is, ‘a dissociation in timing
between individual developmental
processes or modules’. This definition
appears at first sight to have a useful
precision, but it widens the potential scope
of heterochrony to encompass all examples
of something occurring or not occurring
because its normal cause has shifted in
time, maybe shifted so much that it never
happens. Developmental biology is replete
with examples of repressive interactions
that prevent the formation of structures
where they are not required, so it follows
that the loss of an interaction can easily lead
to the formation of heterotopic structures.
But this means that the distinction between
heterochrony and heterotopia has been lost.
Second, there is the unfortunate fact
that timing is one of the aspects of
development that is least well understood
by developmental biologists. We simply
have no idea how events can be
programmed to occur at times that are
long relative to biochemical events or
to the cell cycle. The other big hole in
contemporary developmental biology is
any real understanding of the control
of size and proportions. Because size,
proportions and timing are the basic raw
material of most morphometric analysis,
it follows that the persistence of a large
gulf between developmental and
evolutionary biology is not surprising.
The book is written for evolutionary
biologists who are familiar with modern
morphometric analysis. It is quite detailed
and would be most useful for a graduate
student or research level readership. At
£74.50 it is unlikely to have significant
sales to individuals, but it would be a
useful acquisition for libraries serving
evolutionary biologists who have an
interest in morphological change.
Jonathan Slack
Developmental Biology Programme, Dept of Biology and Biochemistry,University of Bath, Bath, UK BA2 7AY.
Reference
1 Gould, S.J. (1977) Ontogeny and Phylogeny,
Harvard University Press
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