LETTERS TO THE EDITORS
Green-Eyed Monster
To the Editors:
I found Christine R. Harris's article "The Evolution of
Jealousy" interesting (January–February). I appreciate
how her comments might encourage better efforts to manage
confounding variables in studies of jealousy. At the same time,
however, it is a curious coincidence that quite disparate kinds of
studies all kept coming to the same conclusion.
Dr. Harris made many comments that suggested she was not fully
informed on the literature on adaptations (or exaptations). Most of
all, before making the claim that jealousy is a general
psychological mechanism, it's important to look closely at the
literature on sexual dimorphism. Human males are, on the whole,
bigger than females. This phenomenon is apparently an evolved
solution to a single conspicuous problem: Males compete with each
other for reproductive opportunity. If this is true, then it seems a
whole host of hormonal differences (that contribute to things like
increased muscle mass and high-risk behavior) are also selected for
the same reason. Moreover, it seems something similar could be said
of human females—that is, lactation, higher body-fat
percentage, the influence of estrogen on oxytocin and so on are also
solutions to a single conspicuous problem: reproduction and the
costs of reproduction.
If these assumptions are correct, then it would be odd that natural
selection would go to all this trouble to create notable physical
and hormonal differences in males and females, yet would leave male
and female psychology alone. If one accepts Dr. Harris's position,
then it seems one must ignore signficant differences in male and
female evolutionary environments. A general mechanism for jealousy
amounts to being a Cartesian dualist: Evolution works only on the
body, not on the brain.
Jordan Burks
University of Dalhousie
Dr. Harris replies:
Dr. Burks confuses the general question of whether there are evolved
sex differences in the human brain with the topic of my article,
which was the merit of one particular hypothesis about a purported
sex difference in jealousy. I never suggested that male and female
brains are identical; certainly there are important differences,
some presumably reflecting different selection pressures on
ancestral men and women. However, this vague a priori
expectation does not mean that proposals for the existence of a
given sex difference should automatically be accepted without
empirical corroboration merely because some reasonable-sounding
Darwinian story is advanced. Such stories are altogether too easy to
make up, even for diametrically opposed traits. As for Dr. Burks's
suggestion that it is a "curious coincidence" that
different types of studies initially supported the theory of innate
sexually dimorphic jealousy, in fact the article offers several
counterexamples. For example, can any test be more straightforward
than asking people who suffered infidelity what they focused on? Yet
this produced data strikingly at variance with the theory.