Genes, Brains, and Human Potential The Science and Ideology of Intelligence

154 INTELLIGENT DEVELOPMENT

DEVELOPMENT AND EVOLUTION

It is natu ral to think of these intelligent developmental pro cesses as

direct products of evolution:

evolution q development.

However, we now know that it can work the other way:

development q evolution.

Th ere are many possibilities. For example, by buff ering development,
canalization allows ge ne tic variation from mutations to accumulate.
Normally, such ge ne tic variation in impor tant functions would be reduced
or eliminated by natu ral se lection. Under canalization, however, it may
be sheltered and consequently accumulate in the genome. (Th is is another
way in which genes that appear to be in de pen dent are actually brought
into highly interactive pro cesses). However, this cryptic ge ne tic diversity
can be subsequently exposed by extreme changes in the environment that
canalization cannot cope with. It might then become available to natu ral
se lection and contribute to further evolution.

initial

attractor

instability

emergence of

new attractors

FIGURE 5.6
A developmental landscape depicted as progression of an initial state (the ball) with the
emergence of new attractors (diff erentiated tissues, organs, individuals, etc.) over time.
(Redrawn from E. Th elen and L. B. Smith, A Dynamic Systems Approach to the Develop-
ment of Cognition and Action [Cambridge, Mass.: MIT Press, 1994].)

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