10 June 2005

Is there a gene for bad argument?

Spirituality Explained? Reflections on Dean Hamer’s The God Gene
This climate propelled Dean Hamer’s The God Gene into some measure of prominence (cover of Time, October 25, 2004). Let’s deal with the title right away. Pretty unequivocal, no? The God Gene! Already on page 8, however, Hamer inserts a disclaimer: “There are probably many different genes involved, rather than just one. And environmental influences are just as important as genetics.” Hamer is nothing if not savvy: this measured estimation is too tepid by half for marketing a book (or making Time’s cover).

What are we to make of Hamer’s retreat from the bold confidence of his title? By invoking environmental influences, does he mean to embrace what anthropologists like me call a social constructionist explanation? That is, does he admit the importance of how we are raised and loved and guided, for explaining why humans everywhere tend to embrace some notion of God, gods, or spirits? (I get really riled when any cultural universal is automatically assumed to be an instinct; cultural factors can explain many universal human behaviors.)

Science writer and blogger Carl Zimmer is unsatisfied with Hamer’s page 8 retreat. He suggests a title that more accurately reflects the book’s contents: A Gene That Accounts for Less Than One Percent of the Variance Found in Scores on Psychological Questionnaires Designed to Measure a Factor Called Self-Transcendence, Which Can Signify Everything from Belonging to the Green Party to Believing in ESP, According to One Unpublished, Unreplicated Study.

To fully understand what Zimmer means by his mock title, it’s important to see the distinction Hamer makes between religion and spirituality. Religion is “belief in a particular God, frequency of prayer, or other orthodox religious doctrines or practices.” Hamer isn’t interested in measuring a tendency to be religious, as it turns out: “If our intent had been to measure religiousness rather than spirituality,” he writes, “…[w]e might have explained how often people attended religious services, for example, or whether they took their children to Sunday school.”

In other words, Hamer conflates religion with a narrow set of institutionalized practices. This is problematic for a huge number of reasons I won’t enumerate here, since Hamer’s focus is on spirituality. Spirituality is self-transcendence, the capacity for experiencing the self at one with the world, and can in turn be measured via a fine-tuned questionnaire that focuses on self-forgetfulness, transpersonal identification, and mysticism. All this jargon aside, the key point for Hamer is that once you’ve got the questionnaire answers, all you need next is... DNA!

Are gender differences predetermined?
Female strengths usually include better verbal skills, precision manual dexterity, emotion decoding and "landmark memory," defined as the ability to recall objects and their locations within a confined space. (Yes, there's research backing up the cliche about men staring into the fridge, asking "Honey, where’s the ketchup?")

If you believe that socialization -- the molding power of our environment -- is the main cause of gender differences, consider this: Berenbaum's data on girls with CAH point to the power of sex hormones, particularly those we're exposed to prenatally, in shaping our choices and aptitudes as children.

As a group, the girls in Berenbaum's study tend to prefer toys more typical for boys, show more interests in sports, have better spatial ability, and show less interest in infants and dolls than girls without CAH. Despite the hormone-balancing medication they've received since birth, exposure to high androgen levels during brain development in-utero seems to have a lasting masculinizing effect.

"The question is 'How does that happen?'" asked Berenbaum. "It's very complex. Despite some of my own data, I certainly wouldn't make a direct equation that hormones cause you to like trucks." And, she added, laughing, there's no dishwashing gene.

"Yes, there's evidence that biology does influence behavior that shows sex differences," said Berenbaum. "It's also true that, for all behaviors studied, the distributions for males and females overlap on a continuum. Nevertheless, the differences are observed consistently."

Don't rule out the impact of socialization on gender though, cautioned Berenbaum. "What happens to most people is that we start out with small biological differences which send us off on different environmental trajectories. Socialization then magnifies the differences until they become bigger over time."

"Let's take interest in babies, for instance," she added. "Say as a girl you have a slightly increased predisposition to be interested in babies. So you hang around babies. You get comfortable with babies. You get lots of rewards for hanging around babies -- getting paid and praised for babysitting -- so after a while, a slight preference becomes a strong interest because it's magnified by the experiences you have."

That close dance between nature and nurture may be what "makes it hard to answer this question" as Berenbaum put it. A self-described feminist who believed, as a grad student in the 1970s, that gender differences would be leveled by changing social norms, Berenbaum is quick to point out that genes -- like anatomy -- are not necessarily destiny.

"I think that some people are afraid to think that genes influence behavior because it therefore means we can't change it, but that's not correct. I would argue that if we know the genes that influence a certain behavior, it might be easier to change them with an environmental intervention because we would know what we'd be targeting.

This stuff gets set up for cartoon debates all the time, where social constructionists argue for nurture alone and biological determinists argue for nature alone. Then someone trots out the reductio ad Hitlerum, throws in a liberal dose of the appeal to consequences, and it all ends in tears.

The obvious answer is some combination of the two and the boundary between them is going to move around a lot over the next couple of decades. Hamer's God gene strikes me as extremely silly, and this would not be the first time Hamer has produced research so qualified, uncertain and poorly sampledas to be meaningless. Barenboim's perspectives strike me as considerably more persuasive and certainly more nuanced.

7 June 2005

Size does matter, but on the other hand...

I seem to have got sucked into a fairly passionate thread on the nature or nurture of sexual orientation at Larvatus Proteo. In the course of trawling up references I discovered a fun comparison of handedness and sexual orientation. The truly daring seeker of knowledge can pile into Sexual orientation and handedness in men and women: a meta-analysis (large PDF).

There's also some slight evidence from Kinsey that gay men have longer penises, but (before you reach for a ruler) the finding is subject to the following caveat:

These findings are open to criticism because the measurements were made by the subjects themselves at home and not by an independent observer. (Gay men might be more tempted to exaggerate than straight men, or they might be more aroused by the sight of their erect penises, thus causing stronger erections.)� If correct, the result is inconsistent with the simplest form of the prenatal hormone hypothesis, which would predict gay men's penises to be smaller. There are various ways one could make the findings fit the hypothesis, but it may not be worth dwelling on this until a replication study has been done - which could be a while.