Adaptation and Natural Selection - G. Williams (Princeton Univ Press, 1996) WW

324 Pages·1996·2.66 MB·English

ADAPTATION
AND NATURAL SELECTION
A Critique of Some Current
Evolutionary Thought

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Preface to the Princeton Science Library edition
copyright © 1996 by Princeton University Press

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Contents

PREFACE (1996) ix

PREFACE xv

1. INTRODUCTION 3

Evolutionary adaptation is a special and onerous con-
cept that should not be used unnecessarily, and an
effect should not be called a function unless it is clearly
produced by design and not by chance. When recog-
nized, adaptation should be attributed to no higher a
level of organization than is demanded by the evidence.
Natural selection is the only acceptable explanation for
the genesis and maintenance of adaptation.

2. NATURAL SELECTION, ADAPTATION, AND
PROGRESS 20

Natural selection can be effective only where there are
certain quantitative relationships among sampling er-
rors, selection coefficients, and rates of random change.
The selection of alternative alleles in Mendelian popula-
tions meets the requirements. Other conceivable kinds
of selection do not. Selection of alternative alleles works
only with an immediate better-vs.-worse among individ-
uals in a population, and the question of population
survival is irrelevant. Once a certain level of complexity
is evolved, selection will maintain adaptation by occa-
sionally substituting one adaptive character for another,
but this will not result in any of the kinds of cumulative
progress that have been envisioned.

V

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CONTENTS

3. NATURAL SELECTION, ECOLOGY, AND
MORPHOGENESIS 56

The gene is selected through a complex interaction with
its environment, which can usefully be considered to
include several levels: the genetic, the somatic, and the
ecological. The ecological has many aspects, one of
which, the "demographic," is given special treatment.
Age-specific birth rates and death rates are important
factors in the selection of developmental rates and other
aspects of life cycles. The importance of genetic assimi-
lation as a creative factor is minimized.

4. GROUP SELECTION 92

Selection at the genie level can produce adaptive organ-
ization of individuals and family groups. Any adaptive
organization of a population must be attributed to the
selection of alternative populations. Reasons are ad-
vanced for doubting, a priori, the effectiveness of such
group selection. Organic adaptations, which function to
maximize the genetic survival of individuals, are distin-
guished from biotic adaptations, which would be de-
signed to perpetuate a population or more inclusive
group.

5. ADAPTATIONS OF THE GENETIC SYSTEM 125

Phenomena relating to the genetic system, such as
dominance, diploidy, sex-determining mechanisms, and
the distribution of sexual and asexual reproduction in
life cycles are easily explained as short-term organic
adaptations. The survival and evolution of groups are
fortuitous consequences of these adaptations and of
their occasional malfunctioning, as in mutation and
introgression. There is no respectable evidence of mech-
anisms for maintaining evolutionary plasticity or of any
other biotic adaptations of the genetic system.
vi

CONTENTS

6. REPRODUCTIVE PHYSIOLOGY AND BEHAVIOR 158

Variations in the intensity of reproductive effort, and
in the manner in which it is expended, seem designed
to maximize the reproductive success of the reproduc-
ing individuals. Attention is given to the evolution of
fecundity, viviparity, gregarious reproduction, and dif-
ferences between the sexes in reproductive behavior.
These phenomena support the conclusion that the goal
of an individual's reproduction is not to perpetuate the
population or species, but to maximize the representa-
tion of its own germ plasm, relative to that of others in
the same population.

7. SOCIAL ADAPTATIONS 193

Selection within a population can lead to cooperative
relations among closely related individuals, because the
benefits of cooperation would go mainly to individuals
with the genetic basis of cooperation, rather than to
those of alternative genetic makeup. Selection at the
genie level thus explains insect societies and analogous
developments in other organisms. Other apparent ex-
amples of altruism are explained as misplaced parental
behavior. They represent imperfections in the mecha-
nisms that normally regulate the timing and execution of
parental behavior. Benefits to groups often arise as in-
cidental statistical consequences of individual activi-
ties, just as harmful effects may accumulate in the same
way.

8. OTHER SUPPOSEDLY GROUP-RELATED
ADAPTATIONS 221

Various supposed biotic adaptations, such as poisonous
flesh, senescence, and genetically heterogeneous somata,
are examined and found to be spurious or inconclusive.
The regulation of population size is shown to arise from
individual adaptations or purely physical principles
rather than as an adaptive organization of the group.
vii

CONTENTS

Similar arguments are used against the concept of an
adaptive organization of ecological communities or more
inclusive entities.

9. THE SCIENTIFIC STUDY OF ADAPTATION 251

For a given biological mechanism there are no estab-
lished principles and procedures for answering the
question, "What is its function?" Objectively deter-
mined answers to such questions would facilitate prog-
ress in many fields of biology, but they must await de-
velopment of special concepts for the study of adapta-
tion as a general principle. Teleonomy is a suitable
name for this special field of study.

LITERATURE CITED 275

INDEX 291

vii i

Preface (1996)

MY FIRST AWARENESS of a motive for Adaptation and Natu-
ral Selection came during the 1954-55 academic year
while on a teaching fellowship at the University of Chi-
cago. The triggering event may have been a lecture by A.
E. Emerson, a renowned ecologist and termite special-
ist. The lecture dealt with what Emerson termed benefi-
cial death, an idea that included August Weismann' theory
that senescence was evolved to cull the old and impaired
from populations so that fitter youthful individuals could
take their places. My reaction was that if Emerson's pre-
sentation was acceptable biology, I would prefer another
calling. Walking home from the lecture with my wife,
Doris, I regaled her with my unhappiness about the lec-
ture and proposed the obvious idea that selection among
individuals in any population would be biased in favor of
the young, as long as the likelihood of living to age x was
greater than to age x + 1.
A broader dissatisfaction arose from what seemed to
be a pervasive inconsistency in the use of the theory of
natural selection. Formal presentations of this theory dealt
with genetic variation among individuals in a population.
Whatever features assisted individuals in their efforts to
survive and reproduce would come to characterize the
population. No other factor that could produce adaptive
change was ever proposed. Yet the adaptations recog-
nized by professional biologists—Emerson, for example—
often related to the group as such, and often required

ix