Why and how have humans developed a type of
consciousness unlike that of other creatures? 
Although targeted at readers already knowledgeable in this area, this
book does a very good job of developing and extending evolutionary theory to
explain our cognitive faculties.

The author’s background in
developmental psychology (in which he holds a doctorate) serves as a solid
platform for this overview of the history of the human brain, including the
evolution of our type of intelligence and the intricate social functioning for
which it serves so well.  Having previously
published over a hundred professional articles and several books, in this work,
Geary gets at what are among the most interesting — and largely unresolved —
issues about being human:  why are we conscious and why do we have
such a well-developed sense of self?

The first chapter is a concise
integration of the facts, themes and arguments that make up the book.  The second chapter covers the basic
processes that underlie the evolution of species, and does so in a thorough but
concise manner. Readers are advised to pay close attention to the first two of
the books’ nine chapters, as a good grasp of these are needed well for an
understanding the later chapters.

Geary explains that our
sophisticated cognitive apparatus, and the way we perceive and process
information about the world, are both understandable products of our evolution
as a species.  Chapter 3 specifically
deals with this hominid evolution.  In
our line as with other species, the three universal selection processes are
active:  climatic change, ecological
pressures such as the interplay of evolving species as they compete for
resources, and social pressures such as access to mating partners.  Increasingly, of course, our species focused
more and more on the pressures of competition with our own kind, both between
and within groups.  Beginning at least
2.5 million years ago, the divergence of Homo
came with fundamental changes in cognitive structure and increases in brain
size.  Improvements in the precision of
social awareness and in the specificity of behavior are also known or inferred
from archaeological evidence.  A
correlation between EQ (encephalization
quotient, ratio of brain volume to body size) and cognitive complexity
becomes apparent when comparing the species to which we are (or were) most
closely related.

Of special interest is Geary’s
discussion of the peaking of our own species’ average EQ about 20,000 or so
years ago.  In fact, he points out,
there has been a drop of 3% to 4% in EQ since then, suggesting, as Geary
explains "The implication is that changes in social organization resulted
in a relaxation of the selection pressures that drove the rapid increase in
EQ" (p. 53); presumably these pressures have been stable in the millennia
since.

The middle section of the book,
Chapters 4 through 7, address issues such as brain organization, the modularity
of mind, the role of heuristics and "controlled problem solving," and
the neurobiology of information processing.

While there is much of interest in
these chapters, Chapter 8 — the most powerful and interesting chapter of the
book, in my opinion — continues this line of thought.  This chapter links the evolution of fluid
intelligence most directly to climatic change over time, and to the evolution
of social relationships. 

Geary posits that human cognitive
structures permit us to mentally "generate a problem space that includes a
representation of the ‘perfect world’" in which we are totally in
control.  In other words, we are an
omnipotent agent in this inner world. 
The real world, obviously, does not generally conform to this mental
world, and the primary mental goal is then "to generate strategies that
will reduce the difference between conditions in the real world and those
simulated in the perfect world, that is to generate ways to gain better control
of important relationships and resources" (p. 301).

Chapter 9, the last of the book,
considers the way society handles the issue of general intelligence.  Referencing well-accepted studies of these
issues, Geary notes that "general intelligence, especially gF [fluid intelligence] evolved to
facilitate competition with other people for social and resource control and it
is still used that way" (p. 336). 

This book develops several lines of
thought about issues that are crucial to understanding human nature.  Readers will find this a rewarding
experience, despite the unavoidably dry and detailed accounts of some of the
foundational material.

© 2005 Keith Harris

Keith
Harris, Ph.D., is a clinical psychologist and supervises the research
section of the Department of Behavioral Health, San Bernardino County,
California. His interests include the empirical basis for psychotherapy
research (and its design), human decision-making processes, and the shaping of
human nature by evolutionary forces.

Categories: Psychology, Genetics