Review of Copeland
& Hamer (1998) "Living with Our Genes"
CBC “Quirks & Quarks” 28
May 1998
“Is it genetic?”
It’s well-known that, if you’re yellow & round (and a pea) and
marry someone green & wrinkled, your baby peas will all be yellow
& round. Your grand peas will be more varied, but some will be as
like you as, well, two peas in a pod. That's Genetics: the science of
sorting out
the rules that govern such family resemblances. Do such rules extend to
humans? We know they do. But do they explain such complex behavioural
and
personality traits as intelligence and sexual orientation?
That’s the
question asked by Dean Hamer, a geneticist at the US National Cancer
Institute, and co-author Peter Copeland, in “Living with Our Genes,”
a
popular account of recent research on the genetics of behavior and
personality. Their answer is, simply, Yes: “People are different because they have
different genes that created different
brains that formed different
personalities.”
Their case is presented in eight chapters called “Thrills,” “Worry,”
“Anger,” “Addiction,” “Sex,” “Thinking,” “Hunger,” and “Aging.”
Hamer &
Copeland try to make the case for direct connections between particular
stretches of DNA and specific
human personality traits. We are told, “Everyone has a ‘mood gene,’ and a ‘sexual
orientation gene,’ and a gene that regulates body weight.”
I have to say that I found their argument unconvincing. The scientific
evidence is oversimplified, and we’re typically told, rather than
shown, what’s so. The presentation is glib, often to the point of
absurdity, and is sometimes downright crude.
Nuryevean leaps
abound. The pervasive influence of genes is illustrated by a pair
of identical twins, separated at birth, who on reunion discover they
are both twice married, first to Lindas then to Bettys, have sons named
Alan, pets named Toy, and identical tastes in smokes and sodas. Studies
of twins are an important method of genetic research, but this kind of
argument is just silly.
. Flat statements
oversimplify complex issues. In “Thinking,”
we’re told, “The evidence that IQ is
largely inherited
is overwhelming.”
Nonsense. There is ample evidence that IQ test scores show high
heritability. Whether there is any single trait called “intelligence”
for such tests to measure is highly debatable. Heritability studies do
not identify specific genes in individuals, they measure the degree of
genetic influence on traits in populations. The interplay of genes and
environment is complex, and a trait that is highly heritable in one
environment may not be at all heritable in another. Heritable traits
can vary enormously between parent and offspring. Heritability is not
inevitability.
The presentation
is by turns reasonable and racy. We read, “Yes,
we are born with a certain genetic makeup. No, that doesn’t mean we
have no control over our lives . . . It’s not nature or nurture,
it’s nature and nurture.”
Quite true. But then we’re told: “[A]
person might have the genetic makeup typical of a mass murderer; but he
could turn out to be the next great professional linebacker.”
Genes undoubtedly
influence behavior and personality, but such crude generalizations
misinform the reader and are dangerous if used as a basis for social
policy. Early
on, Hamer & Copeland dismiss the theory of environmental
determinism, the idea that ”environmental
influences
[are] the only thing necessary to understand a human being.”
This, they say, is “not only stupid
but cruel.” The same can be said of theories of genetic
determinism, and of this book.
For Quirks and
Quarks, I’m Steve Carr in St. John’s.