In The Agile Gene Matt Ridley develops
several interrelated themes. The dominant one, which gives the book its title,
is that genes are not static elements in the processes of life. Many thinkers
think of the genome as a static "blueprint" for living entities. They
are wrong. Ridley, through many examples, shows that the genome is an amazingly
dynamic structure, responding sensitively to the environmental circumstances (both
internal and external) of the living forms of which it is a part.

An important secondary theme is the absurdity of
the "nature vs nurture" debate. Of course, all of life is a product
of both nature and nurture. All of life’s processes involve an interaction between
a genome and an environment. Everyone realizes and admits this; and yet, it is
typical that as soon as this realization is admitted, many thinkers promptly
develop arguments where one or the other of these two themes is given
prominence. Ridley clearly, and in detail, shows both the futility and
destructiveness of such approaches.

The final and most subtle theme that Ridley
develops is a critique of the idea of linear chains of cause and effect. In
general, cause and effect is a circular and very complex process. This applies
even in sciences like physics and chemistry, but it is especially true in
biology. Yet, it is very common (especially in the Nature vs. Nurture
opposition) to assume that each effect has only one cause. Ridley lays such
approaches to rest as both inadequate and misleading.

In the course of laying out his argument Ridley
also reveals the astonishing capabilities of contemporary biological science.
He describes for instance how nerve cells grow through the brain, from a
starting point (for instance, the olfactory bulb in a mouse) to the place where
those nerves interact with other nerves so that a smell is meaningful (to the
mouse). This is amazing stuff, showing that the propagating nerve itself is
exquisitely sensitive to its immediate environment as it grows, first detecting
which way to go, and then detecting the other nerves in the brain (among
trillions of others) that is its target. This whole process is mediated by the
genes in the nerve, that are turned on and off by cues from its environment,
and that cause it therefore to do different things.

Other studies, of twins, elucidate the intricate
interaction of both nature (ie an individual’s genetic heritage) and nurture
(i.e. the way they are raised and educated, and the individual’s life
experiences) in the creation of an adult. One interesting conclusion: one’s
childhood companions have more influence on one than do one’s parents. But, as
always, the processes are all very circular and complex. One’s reactions to
one’s companions have a very large genetic component. The genes that are
effective at any one time are greatly influenced by one’s social circumstances.
A person’s parents have a large influence on both that person’s genetic
structure and on their companions. This is very complex stuff that is not well
understood when one takes intellectual shortcuts.

Ridley is a very erudite, clear, and witty
writer. The Agile Gene is a pleasure to read. I hope that many readers
will share the pleasure, and the knowledge, that he provides.

© 2005 Martin Hunt

Martin
Hunt is an artist living and working in Vancouver, Canada. His work is inspired by math and science. Lately he’s
been indulging an interest in evolutionary theory and its relation to
consciousness.

Categories: Genetics