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

REAL GENES, REAL INTELLIGENCE 129

In fact, many stressful eff ects in the parental environment are now
suspected to cross generations in that way. Even eff ects of experiences
preceding pregnancy can sometimes seem be passed on to off spring: for
example, in humans, a child’s future risk of obesity, diseases such as
diabetes, poor response to stress, and a general anxiety- prone behavioral
tendency.
It needs to be said that these observations are tentative and mecha-
nisms not always clear. At least some are now known to arise from chem-
ical tags placed on the DNA to silence certain genes: a kind of memory
of experience then passed on to the next generation through the mother’s
eggs.^21 Again, the molecular architecture of a whole developmental sys-
tem, itself a product of evolution, is “instructing” the genes, rather than
vice versa. In an article in Proceedings of the National Acad emy of Sciences
(2012), John Mattick reported that this maternal epige ne tic inheritance
is far more widespread and general than previously thought. He said it is
“rocking the foundations of molecular ge ne tics.” And Denis Noble agrees
that “its implications are profound for biological science in general.”^22
Note that this environmental source of variation will appear in the
behavioral ge ne tics twin- study statistics as ge ne tic variation: quite prob-
ably another way in which heritability estimates are distorted.

REPAIRING AND ALTERING GENE SEQUENCES

In the standard model, the crucial information for development and

variation is in the genes. It may be altered accidentally by mutations, or its

expression attenuated by favorable or unfavorable environments. But that

picture is too simple. Gene sequences are, indeed, occasionally damaged

through the commotion and bustle of molecular activity, and mistakes

can be made during cell division and replication. However, the signaling

networks can sense the damage and its dangers, and relay this informa-

tion throughout the cell. Metabolic pathways can then be redirected to

promote DNA repair. Again, this is not the genes in charge but a global

cellular intelligence.

Even more surprisingly, gene sequences, we now know, can be de-

liberately modifi ed (mutated) during development by the demands of

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