5 - Genes and malleability

Summary

Best-selling novels rarely have unhappy endings; similarly, books about genetics and social science usually close with some kind of sugarcoating about how biological traits are not really determined, or how a heritable trait is malleable.

David C. Rowe

It is not true that everyone can reach the same academic standards if provided with adequate opportunity, and the heritability of IQ is a partial measure of that untruth.

John Thoday

GENETIC AND ENVIRONMENTAL CAUSATION

Can phenotypic differences arising from genetic differences be eliminated as easily as environmentally caused differences? Those who answer this question in the affirmative like to point out that being caused by genes does not entail being unchangeable, fixed, or predestined. This trivial truth is easily granted. But after we concede that, indeed, “heritable” does not mean “unchangeable,” there is a temptation to make another step from this truism to a much stronger claim, namely that there is no difference at all between the ways genetic and environmental effects are modifiable. This is a step from truth to falsity.

Let us begin with quotations from Jencks, Dawkins, and Lewontin, which make the same point and initially sound very plausible:

Most of us assume that it is harder to offset the effects of genetic disadvantages than environmental disadvantages. Because our genes are essentially immutable, we assume that their consequences are immutable too. Because the environment is mutable, we assume that its effects are equally mutable. But there is no necessary relationship between the mutability of causes and the mutability of their effects.

(Jencks 1988: 523)