sexual selection

Schizophrenia/Autism Gendered? Really?

Posted by figleaf | Tags:
Wed, 2008-11-12 20:57

Benedict Carey, science reporter for The New York Times has an article that lots of largely dissatisfied people are linking to, about a, um, novel hypothesis that autism and schizophrenia might result from gendered expression of a single gene.

Here are the two most commonly quoted paragraphs

Their idea is, in broad outline, straightforward. Dr. Crespi and Dr. Badcock propose that an evolutionary tug of war between genes from the father’s sperm and the mother’s egg can, in effect, tip brain development in one of two ways. A strong bias toward the father pushes a developing brain along the autistic spectrum, toward a fascination with objects, patterns, mechanical systems, at the expense of social development. A bias toward the mother moves the growing brain along what the researchers call the psychotic spectrum, toward hypersensitivity to mood, their own and others’. This, according to the theory, increases a child’s risk of developing schizophrenia later on, as well as mood problems like bipolar disorder and depression.

In short: autism and schizophrenia represent opposite ends of a spectrum that includes most, if not all, psychiatric and developmental brain disorders. The theory has no use for psychiatry’s many separate categories for disorders, and it would give genetic findings an entirely new dimension.

Read all about it here.

I think it’s reasonably well-established that selection-based dynamics between male and female copies of genes can determine the development, size, or even behavior of offspring. Carey cites two probable cases in humans, one affecting infant size (when the mother’s version of a gene is recessive her pre-birth babies can be much bigger and smaller if her gene is dominant; another candidate might lead to an offspring being higher or lower maintenance.) Thing is that while those effects are determined by the sex of the dominant gene they aren’t gendered: the effects are pretty much the same whether the offspring is male or female.

What Crespi and Badcock are proposing, however, is that the outcomes are gendered. And more to the point, gendered in ways that are specific to contemporary human behavior. I’m really skeptical about that.

Again, leaving aside practical questions like, oh, I don’t know, maybe that autism and schizophrenia can both show up in one person, which kind of cocks up a gendered-expression hypothesis, there are others that are… well, they’re practical too.

For instance if a well-managed “autism gene” produced more “manly” male offspring, and if “manliness” made male offspring more reproductively successful** then supporting those traits would be in the reproductive interest of both the mother and father. So what would be the point of their genes competing? Same for female offspring and well-balanced “schizophrenia” genes.

For instance, going a step further, why assume it’s the male version of the gene that would produce more “manliness?” Or the mother’s copy of the gene that bolstered “femininity?” Again is there any reason to believe that a mother wouldn’t be at least as well-off with more “manly” son? Or that a father’s daughter would have better reproductive success if she was more “feminine?” I’m not saying those are beneficial, just that even if they were it’s not clear why one parent would benefit more than the other, or why male fathers would necessarily code for male characteristics. (Remember also, in humans sex is determined by the male’s X or Y chromosome, not the females XX chromosomes. Even more reason to doubt why the father’s genes, in particular, would discriminate more than the mother’s would when it comes to gendered behavior.)

And then there’s the problem of determining how dynamics among copies of the same gene, which necessarily have to be on chromosomes that are shared by both parents, could affect outcomes expressed by activity on the non-shared male or female chromosomes.

Oh, and finally is it really the case that socialization is unnecessary in boys? Really? No use at all in, oh, say, the ability to read the emotional state of a stereotypical adversary in order to determine whether to attack, negotiate, flee, or even recruit and lead? Really? And given that maternal groups forage up to 90% of the calories and construct more than half the infrastructure in the hunter-gatherer groups that were the dominant social organization for most of human evolution is the handwork and attention to objects that’s often so exaggerated in people with autism really of no benefit to female offspring?

And finally? Genes that would differentially affect something like the robustness of a child (or, since I think research has been done on those lines too, on peas) of vegetable seeds have had a very long time to work themselves out. Something like schizophrenia/autism, though, that would tend to benefit mainly the stereotypically-assumed, gendered behavior of recently-evolved humans though? That’s a very sophisticated development and (since, remember, both parents ought to benefit) an extremely subtle one. That doesn’t seem like a whole lot of time for what would surely require a whole lot of evolution since humans branched off from common ancestors, or, for that matter, since primates branched off from… whatever we branched off from.

Anyway, all this is by way of saying while I think there’s some merit to the idea of looking for behavioral and developmental patterns that are affected by dynamics between male and female copies of genes there’s another paragraph in the Times Article that ought to be quoted more often…

“The reality, and I think both of the authors would agree, is that many of the details of their theory are going to be wrong; and it is, at this point, just a theory,” said Dr. Matthew Belmonte, a neuroscientist at Cornell University. “But the idea is plausible. And it gives researchers a great opportunity for hypothesis generation, which I think can shake up the field in good ways.”

In other words, it’s an interesting area to try exploring, especially behavior or development that’s affected by gene dynamics but provides benefits or harms regardless of the sex of the offspring. But the researchers are probably barking up the wrong tree about their theory that schizophrenia/autism has a gender component… and possibly barking up the wrong forest if they think such gendered expressions are common at all.

[** Remember, for evolution to work it’s not enough for you to have lots of offspring. If they don’t also have offspring then evolutionarily speaking your genes aren’t successful. —fl]

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Sexist assumptions, evolutionary psychology and ovulating women's walks

Posted by figleaf | Tags:
Fri, 2007-11-16 23:37

Summary: It’s commonly assumed men’s orgasms make evolutionary sense but women’s don’t. I propose a counter hypothesis that’s at least as testable as the average evolutionary psychologists’... and makes men’s orgasms a byproduct.

Echidne Echidne of the Snakes asks one of the most relevant questions in contemporary pop science:

Is it the researchers of evolution who seem to be almost totally interested in only one topic: women’s bodies and how women walk or don’t walk and which types of women men might want to mate with? Or is it the popularizers who do this?

I’m not a zoologist, but the focus on women’s properties suggests that these researchers think men are the sex which does the choosing. Yet in most of the evolutionary psychology literature I’ve read the argument is that prehistoric women did the picking. Or is it whatever is most convenient?

Echidne’s permalinks are slow and I’ve nicked the whole post but if you’re patient you can read it in context here.

One obvious answer is that nobody studies men because men’s sexuality is supposedly a) almost universally believed to be “normal” against which women’s sexuality is supposedly “other,” b) that men’s sexuality is utterly uncomplicated, and c) that except maybe for premature ejaculation early on, impotence later in life, and a bizarre attraction to evolutionary-psychology that repels potential female partners men’s sexuality is utterly reliable. (That this isn’t actually true despite that near-universal agreement is a fascinating story in and of itself.) Thus, men aren’t studied because people assume they already have all the answers.

A second possibility: I studied a lot of history and philosophy of science in college with an emphasis on controversies in science and public perceptions of science. One short answer is that, sort of like natural selection itself, there are tens of thousands of papers, articles, and books published a year… and only the “interesting” ones tend to get picked up and passed along.

For what its worth they don’t even have to be current — if they’re nice and juicy they just keep coming back, sometimes year after year. In fact they don’t even have to be true! Last February, for instance, a bunch of concerned bloggers revisited a 2003 hoax report linking fellatio to reduced breast cancer risk.

The point being that we tend not to hear about good human ev-psych (assuming there is any!) because it’s almost guaranteed not to be “interesting.” Where interesting means “sexy,” or, even better, “controversial.”

Note: Bad or controversial memes (which is probably a more appropriate term) actually benefit from twice as much distribution — first from people titillated by it, then by those who deplore it… and, come to think of it, once again by those who debunk it!

—-

As with Ev-Psych the science in Science Fiction is often total junk science but it’s great social-theory fodder. Hannah Arendt made the interesting proposition that Science Fiction has merit for serious thinkers because it acts as a sort of “futures market” for what people believe they can look forward to. Sadly EvPsych is of somewhat less interest because it reveals only what people have believed for generations.

On the other hand, like other forms of fiction it’s a fun genre to play around with. And since I, no less than you, are just as qualified as any popular “authority” I enjoy making up my own theories that fit my own pet biases.

For instance: DrDick mentioned issues with large infant heads and birth canals. Someone else mentioned that real evolutionary behaviorists study animal models. In conversation with one (female) biologist I learned that in quite a few of the species associated with male iconography (bulls, stallions, elk, for instance, and also lions, dogs, and cats) male orgasm isn’t as big a deal, at all, as it is in humans. Instead the urge to copulate for both males and females is more like an itch and ejaculation more like a sneeze. If we anthropomorphize to animals we assume male moose “risk all” for the same mind-blowing orgasms men can experience… but! If other organisms are any indication male orgasms are completely unnecessary.

So! Assuming human male sexuality is the baseline not just for all humans but all male animals… is dead wrong. And if it’s dead wrong then you can ask well, so if whopper male orgasms aren’t necessary for reproduction (340,000,000 wildebeest can’t be wrong) then where do they come from?!?!

Now remember this is all might-as-well-be-conspiracy-theory speculation (just like “real” EvPsych theorizing) but! Back to those big heads and birth canals: when a baby’s head comes pounding through the pelvis the urethra is easily crushed against the underside of the pubic bone. Crushed urethra means serious risk of postpartum bladder rupture, which in turn means no survival to reproduce again. Turns out the large interior of the clitoris wraps around the urethra in just the right spot though.

Coincidence? Maybe. Sort of. Since evolution is not a plan but simply about what one survives, it’s possible that women with larger clitoral tissue right there didn’t have better sex for it but did have better postpartum survival. Boom. Selective pressure out and, considering survival rates, pretty intense selective pressure. The trick? Again, evolution isn’t a plan, and since genital tissue isn’t really specified by anything on the X chromosomes both female and male tissue might be bolstered. Now. One last time, evolution is not a plan.

Clitorises, like penises, are complex systems of nerve and erectile tissue. Genetically speaking the easiest way to grow more padding around the urethra would be to grow the whole shebang and that would include nerves… and nerve paths to the brain. With me so far? Here’s where the speculation game gets really fun: the clitoris gets bigger to mitigate damage by an infant’s skull but all that extra nervous tissue, along with pathways to the brain, might account for why men (who share that tissue) have such whopping, why-bother-it’s-so-obvious orgasm. And why women, unlike most other female mammals, can have bell-ringing orgasms as well. Yes, the capacity for gigantic orgasms could be selected for; no, the selection pressure could have nothing to do with sexual or mate selection. At all!

And yet… for reasons speculated upon in your post and other comments to it, that line of inquiry, which I propose lightly but not at all frivolously, will not be pursued by evolutionary psychologists because, unlike the genre of EvPsych as a whole, it does not buttress all the dominant paradigms about male class, privilege, dominance, and centrality.

Or in news items about them.

[Note: I previously speculation that men’s and women’s orgasms could be a side-effect of an entirely different kind of selective pressure in this post. Again I’m not saying it’s true but it does nicely illustrate the way real evolution with all its contingencies and expediencies work compared to the sort of deterministic/plan-for-everything way we tend to imagine. —fl]

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Hooters, peepers, and evolution

Posted by figleaf | Tags:
Mon, 2007-07-16 10:16

Sam Sugar of SugarBank is as puzzled as I am why so many men are drawn to women with larger breasts.

Until very recently, it was a mystery to evolutionary psychology why men prefer women with large breasts, since the size of a woman’s breasts has no relationship to her ability to lactate. But Harvard anthropologist Frank Marlowe contends that larger, and hence heavier, breasts sag more conspicuously with age than do smaller breasts. Thus they make it easier for men to judge a woman’s age (and her reproductive value) by sight—suggesting why men find women with large breasts more attractive.

Stephen J. Dubner is calling BS and says:

I would think that, even during the Stone Age, if a man had to resort to judging a woman’s age by the relative sag of her breasts instead of a number of other signifiers, he probably wasn’t the kind of fellow who was going to successfully reproduce anyway.

...

Besides if breasts are a clue to age and men are more attracted to more fertile (i.e. younger) women, the ideal breasts would be small and pert which indicate sexual maturity and youth simultaneously. The research says most men go for bigger though.

Read the quote in context here

I know evolutionary psychology (which in practice seems to be unto Sociobiology as Intelligent Design is unto Creationism) is a personal bugaboo of mine but stuff like requiring sexual/reproductive reasons for preferring one type of breast over another. It’s especially galling because, as Steven Dubner points out, most of the proposed solutions require humans in general and men in particular to be really, really, really stupid. And I mean stupid stupid, not just frat-boy-on-a-bender stupid or even contestant-on-The-Darwin-Awards stupid.

And don’t get me wrong, I’m not saying there are no, none, nada, nix, zilch naturally selected behaviors at work between men and women. I’m just saying they have to meet a degree of sophistication at least equivalent to the greater and lesser primates to whom we’re taxonomically related. And as far as I know not even proto-primates like the tarsiers [See photo at right —fl] are that poorly socially organized that something like slightly bigger boobs would be a sufficiently critical discriminant in mate selection for selective pressure to overcome what even to this day is proportionately extreme variability.

Actually I’m more puzzled about why people keep telling each other we prefer bigger breasts when there’s so little actual evidence. For instance the previous links are taken from high in Ask-Men’s top-99 “most desirable women” list — yet all are quite a bit smaller-breasted than many of the women who appeared lower in the list.)

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