Championing the ascent of
reptiles as much as the descent of man, this thoughtful volume on the evolution
of intelligence by Skoyles and Sagan is a welcome addition to the nature/nurture
neurophilosophy shelf. The authors take us well beyond the ‘usual suspects’
listing of gross anatomical brain structure and function of the familiar phyla,
traveling a welcome breadth of comparative data to include a wide variety of
species (including our earlier selves). Rather than merely outline the familiar
shopping list(s) of evolving structures culminating in the development of the
modern human cerebral cortex, Skoyles & Sagan do not end with the
discussion of its distinctive "associative" or "silent"
areas of the brain of old (as so many other authors are still content to do).
Instead, and throughout the book’s eighteen chapters, we are treated to a
series of detailed proposals concerned with the continuously adaptive neural
architecture of both the intra- and inter-cerebral structures underlying the
evolution human intelligent behavior.

Reminiscent of learning the
names of Tolstoy’s characters in the early pages of ‘War & Peace’, one
meets here parts of the brain rarely mentioned (let alone claimed to be of any
significance in explaining who we are and why we behave as we do). Following
the publication of this volume, the long overdue and normally restricted cast
of human brain features will now include the structure and functional
connectivities of the anterior cingulate, the amygdala, the insula, the orbital
and dorsolateral prefrontal cortex of the brain (and these are just a few of
the characters amongst many others that might have been introduced here). We
may still not be able to agree upon how best to measure intelligence (IQ, in my
view, still tautologically measuring ‘what IQ tests measure’), but the
physiological substrates of the brain supporting intelligent behavior are
slowly coming to be located and characterized. Many of the examples and
theoretical components put forward may perhaps appear predictable to those
familiar with modern paradigms in comparative psychology and the study of
intelligent systems (both biological and man-made), but the real strength of
this book is to be seen in its successfully discussing adaptive neural systems
for the technical non-specialist. The story as told here is a great achievement
for a book aimed at the popular science reader.

The basic thesis of the book
follows the development of the nervous system in the aftermath of the ‘KT
event’ (coincident with the demise of the reptilian dinosaurs), which favored
flexible, mobile species with nocturnal, cold-adaptable behaviors, capable of
finding shelter and forage. In contrast, species with relatively reflexive
nervous systems, whilst satisfactory when situated in a stable, predictable
environment, can often fail to adapt to changes within the time course of
sudden catastrophic events. En route to the architecture of the modern human
brain, we meet the aetiology of social and emotional life and their associated
neural substrata in the prefrontal cerebral and limbic cortex (amongst other
structures). The level of neuroanatomical detail is sufficient to provide a
coherent and consistent story of successive adaptations leading to the
development of ‘higher intelligence’, but the pathway taken argues not for this
result deriving solely from phylogenetic mutation (per se), but, and more
importantly, from ontogenetic neural plasticity and enculturation despite the SAME
genetic makeup.

If this idea is new, and at
first glance appears to be an uncomfortable one, don’t panic! If the authors
are right, your prefrontal brain cortex will soon get to work in generating
some reflex inhibition, allowing one to assess (and reassess) the situation,
temporarily delay one’s actions, and then to organize and activate novel
planned behaviors towards worked goals. Whether the modern human can prove
him/herself to be intelligent enough to plan the survival of any future
catastrophe (whether it be of our own making or another KT-like event) we will
have to wait and see. In the meantime we have in this book, an accessible
version of a still-emerging story telling how, and as the solution to what
challenges, the intelligence of a variety of species (including modern humans)
currently evolved to demonstrate.

Excellently referenced
throughout, with bibliography aplenty for those wishing to read more of the
detailed research literature, my only gripe with this book would be with its
lack of visualization aids for those unfamiliar with the brain areas mentioned.
Although the text is sufficiently detailed to allow the reader to construct
crude schematics for him/herself (as one may have done in the case of Tolstoy’s
family trees?), both anatomical and flowchart illustrations might be of help in
hastening the orientation of those perhaps new to the anatomy and
neurophysiology of the brain.

Whether this would indeed
have been the book that Carl Sagan would have written in 1977 had he possessed
the vast corpus of knowledge concerning the brain now available, one may only
guess? It is my own view that Skoyles & Sagan’s title serves more than to
merely pay homage to ‘The Dragons of Eden’, in whose memory this book is in
part written.

©
2002 Anthony Dickinson

Tony Dickinson, McDonnell
Center for Higher Brain Function, Washington University School of Medicine, St.
Louis.

Categories: Genetics, General