BOOK REVIEW
Evo Devo Psych
Ethan Remmel
Origins of the Social Mind: Evolutionary Psychology and Child
Development. Edited by Bruce J. Ellis and David F. Bjorklund.
xviii + 540 pp. Guilford Press, 2005. $65.
Fifteen years ago, the application of principles of evolutionary
biology to psychology was still new and unfamiliar to most
psychologists. That changed with the publication in 1992 of The
Adapted Mind (edited by Jerome Barkow, Leda Cosmides and
John Tooby), which established evolutionary psychology as a
progressive research program. Evolutionary psychologists take the
view that "human nature" is a collection of specialized
psychological mechanisms that proved beneficial in our ancestral environment.
Today, evolutionary developmental psychology is as new and
unfamiliar as evolutionary psychology was 15 years ago. Bruce J.
Ellis and David F. Bjorklund, the editors of a new book on the
subject, Origins of the Social Mind, see this new subfield
not simply as an expansion of evolutionary psychology into the
developmental realm, but as an integration of developmental and
evolutionary thinking. They came to this intersection from different
directions: Ellis trained with David Buss, a noted evolutionary
social psychologist, and then turned to consider developmental
questions, whereas Bjorklund started out as a developmental
psychologist, became a well-known expert in cognitive development
and then incorporated an evolutionary perspective in his work.
Unlike most other subfields of psychology, which typically focus on
particular phenomena (cognitive psychologists study cognition,
social psychologists study social processes, and so on),
developmental psychology and evolutionary psychology do not have
separate domains. Rather, they represent different approaches to the
study of all psychological phenomena. Cognitive processes, for
example, can be investigated from a developmental perspective (as in
the work of Jean Piaget) or from an evolutionary one (as in the work
of Cosmides and Tooby). Integrating the two viewpoints is easier
said than done. Developmental psychologists, who study how behavior
and cognition change with age, focus on ontogeny, the development of
the individual. In contrast, evolutionary psychologists focus on
phylogeny, the development of the species.
Furthermore, developmental psychologists concentrate on proximate
causes—how biological and environmental factors interact to
influence behavior over the life of the individual. In contrast,
evolutionary psychologists focus on ultimate causes—the
reasons that certain behaviors were selected for over the history of
the species—and explain behavior with reference to its
function in the distant past. Evolutionary developmental
psychologists need to consider both proximate and ultimate causes.
With few exceptions (such as John Bowlby's hypothesis that
specialized psychological mechanisms have evolved for forming
strong emotional attachments between caregivers and infants, and Jay
Belsky's argument that a child's early family environment provides
cues as to which reproductive strategy will be most adaptive in
adolescence and adulthood), mainstream developmental psychology has
not been very informed by evolutionary theory. And evolutionary
psychologists have often limited themselves to the study of adults,
thus missing out on developmental psychology. A major step toward a
rapprochement was the publication in 2002 of The Origins of
Human Nature: Evolutionary Developmental Psychology, by
Bjorklund and Anthony D. Pellegrini.
Origins of the Social Mind takes another step in that
direction, assembling a critical mass of authors who have both
developmental and evolutionary interests. The book consists of 19
contributed chapters, organized into three sections—on general
theoretical issues, personality and social development, and
cognitive development. The text is long (more than 500 pages) and
written in a technical style with lots of citations. Definitely
pitched for an academic audience, this is not a book that people
outside psychology are likely to pick up and read cover-to-cover for
fun. For an accessible introduction to evolutionary developmental
psychology, The Origins of Human Nature is a better bet.
The editors try to tie Origins of the Social Mind together
by providing a nice introductory chapter, an index and some
references within chapters to other chapters. However, the chapters
really vary in content and approach, reflecting the fact that
evolutionary developmental psychology is still coalescing as a
research program. Some of them are rather rambling reviews of
developmental research in a particular area, with evolutionary
speculations sprinkled on top. These chapters, in which existing
developmental data are reinterpreted in the light of evolutionary
theory, may provide useful references for people already interested
in those areas of research, but they don't always make fascinating
reading. The more successful chapters are organized around an
argument rather than an area of study, venturing a provocative
hypothesis and presenting new research designed to test it.
In one such chapter, Jay Belsky describes his "differential
susceptibility hypothesis"—that is, the idea that
children vary in their responsiveness to early environmental
influences such as parenting. Belsky offers an evolutionary argument
for why such variation would be adaptive, and he provides some
empirical evidence in support, including some new analyses of the
data set of the National Institute of Child Health and Human
Development Study of Early Child Care.
In another interesting chapter, Jesse M. Bering argues that
religious beliefs may be prevalent because they are adaptive, in
that they promote prosocial behavior—that is, they provide a
motivation to behave well even when no other person is looking:
because God or some other supernatural agent may be watching.
[Editor's note: See feature article by Bering in
this issue.] Bering suggests that evolved psychological
mechanisms account for people's tendency to attribute coincidences
to supernatural agency, and he presents new developmental data
consistent with this hypothesis.
In a chapter on empathizing, Simon Baron-Cohen summarizes evidence
in favor of his "extreme male brain" theory of autism (a
"male brain" being one in which systemizing is more
developed than empathizing). The evolutionary argument for sexual
variation in brain types is only sketched here; it is discussed at
greater length in his 2003 book The Essential Difference: The
Truth about the Male and Female Brain.
Among the weaker contributions, a chapter by Glenn E. Weisfeld and
Heather C. Janisse illustrates the sort of Panglossian thinking
(assuming that every characteristic is adaptive) for which
evolutionary psychology is sometimes criticized. Weisfeld and
Janisse even suggest that male nipples—the classic example of
a biological spandrel, or evolutionary by-product (in this case, of
female nipples)—"may function to attract or reassure
infants" (no evidence for this claim is provided). They also
make a number of other dubious claims, such as this one:
"Before puberty, the sexes are quite similar." It's hard
to believe that anyone who has spent time around children would say
such a thing, and it is directly contradicted by data discussed in
other chapters. However, Weisfeld and Janisse don't have a monopoly
on dubious claims. In his chapter, Brian MacWhinney suggests that
"individuals with high levels of imitative skill are likely to
attract mates by entrancing their attention" (again, no
evidence is provided). Imitating a prospective mate is sexy? Maybe,
but I'm not going to try it on my next date.
One of the most interesting questions for evolutionary developmental
psychology is whether childhood itself is an adaptation: Is the
extended period of psychological immaturity in humans just an
inevitable by-product of the fact that it takes us a long time to
reach adulthood, or is it actually more beneficial than a faster
rate of development would be? This issue is addressed in several
chapters, especially one by Mark V. Flinn and Carol V. Ward and
another by Bjorklund and Justin S. Rosenberg. These authors
acknowledge that there are some biological constraints on the system
(for example, fetal brain size versus female hip width) but argue
that an extended childhood is actually adaptive, because it allows
time to develop the social-cognitive skills necessary to master the
specifics of children's social environments. However, their argument
assumes that ancestral social environments were varied enough for a
"tuning" period to be beneficial and that a slower rate of
social-cognitive development was selected over faster alternatives.
It might just be that children develop as fast as is biologically
possible. Such questions should keep evolutionary developmental
psychologists busy for a while.
So has an evolutionary perspective taken over developmental
psychology? Certainly not yet. A look at the indexes for the
programs from the last three biennial meetings of the Society for
Research in Child Development (the leading professional organization
for developmental psychologists) turns up only a couple of items
pertaining to evolution. Will the evolutionary perspective become
dominant within developmental psychology eventually? I wouldn't bet
against it, for the same reason I wouldn't bet against evolutionary
psychology in general—a lack of alternatives. Evolutionary
psychology has a lot of problems—claims that run ahead of the
evidence, misunderstandings and oversimplifications of evolutionary
biology, and the perception that the approach provides scientific
cover for stereotypical attitudes toward the sexes. Nevertheless, it
continues to attract adherents and is arguably the most progressive
paradigm in psychology today. (It just goes to show that, in
science, relative promise can be more important than current
evidence.) Evolutionary psychology has the potential to unify our
understanding of psychological phenomena under one theoretical
umbrella and faces little competition for that role.
The only contender of similar scope is developmental systems theory,
which argues that adult structure is not encoded in the genes but
rather emerges through the interaction of each organism with its
environment. Developmental systems theorists criticize evolutionary
psychology's model of development—that genes determine the
range of options from which environment selects (the
"jukebox" metaphor)—as overly deterministic.
However, developmental systems theory can be criticized as not
deterministic enough. By emphasizing the unique complexity of every
individual, the theory risks reducing psychology to biography. Some
generalization and simplification are necessary for a theory to gain
predictive purchase. In any event, Bjorklund argues that answers to
the developmental systems theorists' critiques can be incorporated
into the framework of evolutionary psychology.
Evolutionary developmental biology, or "evo devo," is
currently a hot topic in biology. Fifteen years from now, we may
look back on the publication of Origins of the Social Mind
as the point when evo devo became a hot topic in psychology.