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Genotype-environment interactions and our understanding of the biological bases
of human cognitive abilities [i]

By Massimo Pigliucci

Abstract

The debate on the biological bases of human characteristics, and especially of
cognitive abilities, has been raging in philosophy and biology essentially
forever. The two extreme positions maintain that either a) the genes of an
individual causally explain most of her characteristics, with the environment
playing a modifier role, or b) the environments (physical but especially
cultural) to which an individual is exposed during her life are the major
determinants of her behavior, with the genes playing a secondary role. There is
indeed convincing evidence to support both positions, but that does not mean
that the truth lies somewhere “in the middle”. Where would this middle be?
Surely nobody think it possible to Solomonically divide an individual’s
intelligence or creativity in percentages due to the environment experienced by
or to the genetic makeup of that individual. I will submit that the conceptual
solution to the conundrum has already been provided by the study of
genotype-environment interactions as understood in the context of the modern
theory of reaction norms and phenotypic plasticity. However, no relevant data
of this type can be obtained for humans because of ethical considerations as
well as technical difficulties. While interesting conclusions can be derived
for other mammals, and possibly even for some primates, the study of nature vs.
nurture in humans is indeed very limited, and it is about time that the
scientific community refrains itself from making grand statements that cannot
be reasonably substantiated by the available evidence. This especially in light
of the obvious implications of such studies for social and educational
policies.

"Men have an extraordinarily erroneous opinion of their position in nature; and
the error is ineradicable."

W. Somerset Maugham (1874–1966), British author. A Writer’s Notebook (1949),
1896 entry.

Science or ideology?

             The debate on the relative importance of nature (genetics) and
nurture (environment) in determining human traits has been prolonged,
acrimonious, and largely pointless. Great minds have engaged in it during the
last 300 years, from philosophers of the like of John Locke and Thomas Hobbes,
to scientists of the caliber of Stephen J. Gould, Richard Lewontin, and Edward
O. Wilson, to social scientists like Arthur Jensen, R.J. Herrnstein and C.
Murray. A great number of books and an even greater number of book reviews,
articles, and media appearances have been devoted to the problem. Gould’s “The
Mismeasure of Man” (1996) echoed Lewontin and colleagues’ “Not in Our Genes”
(1984) , while Wilson had previously published “On Human Nature” (1978) , and
Herrnstein & Murray subsequently produced “The Bell Curve” (1994) . They are
all largely unfounded on scientific grounds and at best provide interesting
speculations. By and large, they all simply reflect the (respectable, yet
largely groundless) opinions of their authors. More precisely, they all
represent the hopes and ideological agendas of their esteemed proponents[ii].

            This claim of mine may seem excessive, or even suicidal in view of
the fame, scientific expertise, and political spectrum of the people I have
mentioned. Yet, anyone familiar with the field of phenotypic plasticity (i.e.,
the way in which a genotype responds to the environment Schlichting and
Pigliucci 1998) in modern evolutionary biology  will know that such a
conclusion must follow from what we know of genotype-environment interactions
in other organisms. My claim is not that we cannot (in principle) know anything
about reaction norms (the function describing genotype-environment
interactions) in humans, or that we do not know anything about genetic or
environmental effects on human characteristics. But I submit that we currently
do not know much that is pertinent to the discussions that these and other
authors have been engaging in, and especially that we know very little that can
sensibly inform our social policies. When eminent scientists in a field can
draw such diametrically opposite conclusions about a given subject matter as
Gould and Wilson do, it is a good bet that they are engaging in an intellectual
exercise that is groundless enough from an empirical standpoint to allow for
such latitude of positions. In this essay I will lay out my argument of why
this is precisely the situation of our current knowledge of the biological
basis of human nature. The reader should be warned that the following is as
much a scientific discussion as it is one about philosophy, ethics, and
politics. As such, and unlike the case of scientific controversies, the
backgrounds and personalities of the characters involved are as relevant a
consideration as their arguments.

Full text:
http://fp.bio.utk.edu/wisdom/Essays/nature-nurture.html

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Ian Pitchford <[log in to unmask]>
Editor, The Human Nature Daily Review
http://human-nature.com/nibbs/
Centre for Psychotherapeutic Studies
School of Health and Related Research
University of Sheffield, S10 2TA, UK
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