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

122 REAL GENES, REAL INTELLIGENCE

We now know of numerous examples of such plasticity. In the journal
Science Signaling in 2012, Nancy Gough gives the example of how one
par tic u lar signaling molecule acts as a coincidence detector, sensitive to
the timing of two other signals. Th e response of the detector, such as
“ca lling up” specifi c gene products, “only occurs if the stimuli producing
the signals are received suffi ciently close together.”^16
Writ large, we have to think of multitudes of enzyme- boosted reac-
tions, with modifi able eff ects on one another and on substrates, the whole
sensitive to the structure of change. Of course, some aspects of the envi-
ronment can be suffi ciently recurrent, even across generations, as to per-
mit predictability without such constant retuning. As with gears in a
machine, some components may be sized or weighted by natu ral se lection
to create biases in signal pro cessing toward par tic u lar endpoints (see the
discussion of the canalization of development in chapter 5). A monkey
will develop a tail whether it grows up in the jungle or a pent house suite—
humans defi nitely not! Many, or even most, of those components, includ-

A

receptors

cell

membrane

genes inside the

nucleus

gene products

from same gene

rearranged

ligands

GHK

BFJE

CD

FIGURE 4.5

Simplifi ed illustration of signaling pathways. Circles A– K are vari ous signaling factors

(of which there can be hundreds in a typical pathway).

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