POTENTIAL IN THE GENE- BRAIN

T

o most people, it seems, potential originates in the genes but devel-
ops in the brain, and there it gives rise to intelligence; that is, the
potential in the genes makes the brain. Th is is also scientifi c ortho-
doxy. As summarized by Toga and Th ompson (see chapter  1), alleged
individual diff erences in potential are “partly mediated by brain struc-
ture that is likewise under strong ge ne tic control. Other factors, such as
the environment, obviously play a role, but the predominant determinant
appears to be ge ne tic.” Th e United Kingdom’s Royal Society says some-
thing similar in its Brain Waves initiative.
In the same groove, behavioral ge ne ticists oft en say that their objec-
tive is to describe the pathways from genes, via brains, to intelligence. Th e
fact that no such pathways exist (at least in that genet ically deterministic
sense) prob ably explains the diffi culty experienced in fi nding them. Un-
fortunately such gene- centered thinking has also obscured what the brain
really does in relation to intelligence. As Robert Plomin and colleagues
say in their book Behavioral Ge ne tics, “It has been diffi cult to connect the
dots between genes, brain, and be hav ior.”^1
Th is chapter aims to explain that diffi culty. Yet again, behavioral ge ne-
ticists have cause and eff ect the wrong way around. We have already seen
how the intelligent systems of the cell create potential; physiological and
developmental systems do likewise under more changeable conditions.
Just as Charles Darwin attributed brainlike activity to the physiology of
plants I will show how brains further evolved from physiology as even

6. HOW THE BRAIN MAKES POTENTIAL

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