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Time Frames. The rethinking of Darwinian evolution and the theory of punctuated equilibria. By Niels Eldredge. New York Simon and Schuster. 1985. 240 pp. figures tables appendix index. $8

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funding for research and for medical assistance based on homophobia.
The reviewer was particularly interested
to read about the intense scrambling and
competition for the control of federal research funding by CDC, National Institutes
of Health, the New York Blood Center, Harvard University, New York Hospital-Cornell
Medical Center, and Sloan-Kettering. The
AIDS patient is totally forgotten in this tug
of war as real sights are set on fame, the
possible Nobel Prize, and, above all, on royalties. Black’s description of the fight between NIH and the Pasteur Institute in Paris
as to which had discovered the LAV or HTLV3 reads like a script from St. Elsewhere.
Several dilemmas are lucidly discussed and
placed in proper perspective, including the
issue of closing gay bathhouses, where it was
suspected that sexual behavior supported unsafe sex practices. For many homosexuals,
however, baths and bars represented freedom from homophobia and outside harassment. The “collision of different worlds:
straight versus gay, scientific versus hedonistic,” is succinctly clarified by the author as
the broad spectrum of concerned groups
worked in their own way to combat the epidemic. Although some readers may object to
Black’s ongoing personal asides, the book
does present the disparate and similar per-
ceptions of and responses to a shared enemy.
The diversity of the AIDS movement, the
range of philosophies and methods employed
by individuals, groups, and institutions, and
the fervent commitment by everyone t o disarm the AIDS virus make this an intriguing
Additional funding, widespread testing,
unnecessary risk-taking, the relationship
with gay life styles and the AIDS virus, the
public backlash, heterosexuals, and AIDS:
these are all presented and discussed to some
extent in the volume, again, making it something more or less for everyone.
Physical anthropologists who are seeking
a scholarly and scientific treatise that focuses on epidemiology, theories of disease
transmission, and the study of immunity
about the virus may be disappointed with the
book, but the reviewer believes that, given
the opportunity, the book is able to prod our
collective concern, raise our professional conscience, and, hopefully, motivate our constructive action to confront an epidemic that
has demonstrated its global reach.
Human Services Program and
Department of Anthropology
California State University
Fullerton, California
OF DARWIN-cohort of Columbia University graduate stuIAN EVOLUTION
By Niles Eldredge.
New York: Simon and Schuster. 1985. 240
pp., figures, tables, appendix, index. $8.95
Creationism’s impact on evolutionary research has been negligible, yet it has accomplished one thing: It has succeeded in goading
evolutionists to write €or the general public.
Ever since McLean v. Arkansas, more evolutionists than ever before have taken to the
popular media to inform the public about
evolution. Some of these popular accounts
are excellent; others do more harm than good.
Time Frames follows in the best tradition
of popular science. It recounts Eldredge’s
story of how “punctuated equilibrium” came
to be and what he thinks it means for modern
evolutionary theory.
Punctuated equilibrium’s beginnings
were inauspicious. During the 1960s, a small
dents set out to study the evolutionary process using the fossil record. Their studies,
like many before them, were conducted under the aegis of the “modern evolutionary
Eldredge focused his studies on Phacops
rana, a middle Devonian trilobite; a u l d
studied Poecilozonites, a Bermudan land
snail; while the rest of this small contingent
of students investigated other fossil invertebrates.
Eldredge went into the field expecting
Phacops to undergo the slow, gradual, adaptive modification predicted by the modern
synthesis. To his surprise, he found little
more than size variation over the entire 8
million year duration of this species, despite
a considerable range of environmental variation. Phacops did show a reduction in the
number of columns of eye lenses, but here
the change was abrupt, not gradual, and did
not correspond to any obvious adaptive fac-
tor. During most of the 8 million years Phacops had 18 columns, and then suddenly 17
columns became the norm. Matters worsened
when he discovered these “evolved” Phacops
in other deposits that preceded the one in
which he first noted the change. Ultimately
he found a transition site out on the periphery of Phacops’ distribution where forms with
both 18 and 17 columns of lenses occurred, as
did forms with hybrid lens arrangements.
Gould and the others obtained similar
results. Stability, not slow gradual change,
dominated the evolutionary history of these
organisms. Change, when and if it occurred,
was abrupt. These observations unsettled
Eldredge (and Gould), for they conflicted with
several key premises of the Darwinian paradigm. They implied that change was not an
inevitable result of evolution and that constant environmental flux did not correspond
to continual adaptive change culminating in
speciation. This suggested to Eldredge that
new species arise by the breakup of the reproductive plexus during geographic isolation (allopartic speciation). When environments do change, however, most species seem
seem to track the environment or to go extinct rather than adapt.
These findings, along with a series of unfolding paradoxes, eventually inspired Eldredge to write a short paper on the
importance of allopatric speciation in invertebrate evolution. Shortly thereafter, he and
Gould collaborated on the controversial and
now classic 1972 paper where they formally
developed the theory of “punctuated equilibrium.” This paper is included as an appendix
to Time Frames.
While this background is important,
Time Frames has an ulterior motive. Eldredge and Gould’s work has been misunderstood so frequently that Eldredge’s mission
is to elucidate precisely what punctuated
equilibrium’s major premises are.
Eldredge’s message is simple and clear.
Punctuated equilibrium is a remarkably
straightforward set of deductions from the
paleontological record. It holds that once a
species evolves, it usually will not undergo
any significant change as it continues its existence. This stability, well-known and ignored by paleontologists, seems to be the rule
rather than the exception and results from
the basic inertia of the evolutionary process.
Stasis is periodically “punctuated” by events
that result in the formation of new species.
The interruption of reproductive cohesion by
geographic isolation imposes intense selec-
tive pressure on isolates; consequently anatomical (and hence adaptive) change is concentrated in brief time periods that result in
the formation of new species. One speciation
is complete, little additional adaptive change
takes place.
Punctuated equilibrium also gives species a status as legitimate actors in the evolutionary process. As discrete reproductive
entities, species have all the important aspects of individuals in a Darwinian sense.
Thus, they participate in evolution as “individuals,’ and are subjected to evolutionary
forces similar to those acting on individuals.
Of these forces, “species selection,” the analogue to natural selection, is the most important in determining the differential success
of species in the game of life.
So egregious is the misunderstanding (or
misrepresentation) of punctuated equilibrium that Eldredge seizes every opportunity
to clarify the record. He points out that he
and Gould did not propose a new theory of
speciation, did not claim to offer a new theory
of evolutionary mechanisms generated directly from paleontological data, did not
equate punctuated equilibrium with Simpson’s “quantum Speciation” or Goldschmidt’s
“hopeful monsters,” did not deny that gradual evolution occurred, did not propose any
new type of selection, did not deny a significant role to adaptation, and did not diminish
Darwin’s contribution t o evolutionary theory. They did challenge the hegemony of the
modern synthesis in explaining macroevolutionary phenomena, did assert that gradual
evolution did not ever seem to get anywhere,
did argue that continual adaptation was not
a likely explanation for life’s diversity, did
suggest a model for the differential success
of species in the game of life, and did claim
that Darwin erred in his notion of what really
happens to organisms when environments
Time Frames is unapologetically partisan. Still, Eldredge manages to indicate areas
where disagreement (even between himself
and Gould) and uncertainty still exists. In
the absence of continual adaptation, what
powers evolutionary trends? What is the relative importance of deterministic (selective)
forces versus stochastic forces in the evolutionary process? Are there species-level analogues to the four forces of evolution that
determine the fate of a species in any given
situation? Is evolution a problem of the modification of adaptive structure?
If Time Frames has any weaknesses, they
stem from writing in this difficult medium.
By minimizing the raw data, Eldredge gives
short shrift to most of the post-1972 tests of
punctuation that demonstrate its remarkable robusticity. While this will not affect the
public’s acceptance of punctuated equilibrium, professionals who disagree with Eldredge will not be assuaged, nor will uncommitted gradualists find the arguments
compelling enough to be persuaded to join
the punctuated equilibrium camp.
A second, but not unexpected, criticism is
that Eldredge adroitly glosses over objections
to punctuated equilibrium. He repeatedly
emphasizes what he and Gould actually said,
takes up cudgels against statements they did
not make, but barely hints a t any of the
substantive criticisms levelled since they first
proposed punctuated equilibrium. In so
doing, the book is far more one-sided than
I n the final analysis, though, Time
Frames is a provocative, well-written, and
delightful book that clearly documents Eldredge’s instrumental role in the development
of “punctuated equilibrium.” For anyone interested in the history and philosophy of science, it also superbly illustrates the processes
Kuhn described in The Structure of Scientific
Department of Anthropology
Portland State University
Portland, Oregon
Eldredge, N, and Gould, SJ (1972) Punctuated equilibria:
An alternative to phyletic gradualism. In: TJ Schopf
(ed): Models in Paleobiology. San Francisco: Freeman,
pp. 82-115.
Kuhn, TS (1962)The Structure of Scientific Revolutions.
Chicago: University of Chicago Press.
OF HUMAN AGEING.A.H. Bit- should therefore be a characteristic of species
tles and K.J. Collins, editors. Cambridge: with low environmental risk. The implicaCambridge University Press. 1986. viii + tions of this model for humans and for homi280 pp., figures, tables, index. $37.50 nid evolution are only briefly suggested.
Other papers in this group deal with cell
cultures, hormonal systems, and insect
Ageing is a nearly universal phenomenon models as sources of information on the agein biology that has attracted wide scientific ing process. Together they show that no sinattention. Despite this interest, very little is gle theory of ageing accounts for all the
known about the biology of ageing. This in- evidence and that the adaptive significance
triguing volume is a n attempt to address a of ageing is still very much open to debate.
variety of theoretical and practical issues in
The second group of papers deals with bioageing research a s applied to humans. Its 16 logical markers in age assessment. Since
papers are the result of a n interdisciplinary many researchers see ageing as part of the
conference held at the University of London overall developmental process, a chapter is
in 1984, with the specific aim of bridging the included on alternative biological age indigap between cellular research and clinical cators in adolescence and on scoring of age
aspects of geriatric medicine. While the cur- for adults. Concerned with the problems of
rent volume is not a comprehensive overview age assessment for paleodemography, Molleof ageing research, it provides a selective son presents a relatively thorough overview
introduction to a broad range of topics in of techniques currently in use for determinhuman ageing.
ing age from skeletal material. Like many
The individual papers comprising the book skeletal biologists, he is careful to stress the
are loosely grouped by topic. The first four potential inaccuracies of all methods, alpapers and the eighth deal with theoretical though he is perhaps overly pessimistic about
aspects of ageing as a n evolutionary process, the utility of microscopic and multivariate
presenting evidence for both stochastic and methods.
developmental genetic theories. In a very inThe last half of the volume is a diverse
teresting introductory paper, Kirkwood and collection of papers on the demography and
Holliday address the troublesome problem of health of ageing populations. The first pair
why ageing should have evolved at all. Using of these examine projections for proportions
the concept of the “disposable soma,” they of the elderly in the populations of the United
argue that it is not energetically efficient for Kingdom and the United States into the next
a n organism to maintain its body beyond the century. While fertility rates have previously
species life expectancy in the wild. Longevity been principal determinants of these propor-
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