On genetic inheritance and sexual assault.

On genetic inheritance and sexual assault.

How does evolution work?

Each child receives genetic information from its parents.  Some of this information conveys distinct traits.  And some of these traits increase the chance that an individual will have children of his or her own.  If those children are also good at having kids, the underlying genetic information will spread.

The DNA sequences that evolution enriches don’t necessarily make a creature better – in fact, they often accomplish the opposite.  A gene that made its bearer 10% happier would not spread through the population.  Happy people are less fearful and more likely to be die in tragic accidents.

800px-JH_Dolph_Cat_Mouse(Infection with Toxoplasma gondii seems to make mice happier.  The parasite produces a rate-limiting enzyme for dopamine synthesis to increase the chance that Toxoplasma-infected mice blithely stroll along and get eaten by a cat.)

All that evolution “wants” is for a gene’s bearer to have children who have children who have children, and so on.  This necessitates survival, yes – you can’t have kids if you’re dead, and in many species, orphaned children are less likely to ever have kids of their own.  But evolution doesn’t need a gene’s bearer to be clever – brainless starfish evolved from a bilaterally symmetric forebear that did have a brain.  Evolution doesn’t need a gene’s bearer to be nice – bullies seem to have plenty of children, and sexual assault is an instinctual mating strategy in many species, including ducks and orangutans.  Maybe humans, too.

So, who controls which genes are passed on?

In most species, whichever parent puts the most effort into raising children gets to choose.

prumIn The Evolution of Beauty, Richard Prum describes the experience of tropical birds, like manakins, who live in regions where food is plentiful.  The female parent raises children entirely on her own – males reside elsewhere in fraternal performance troupes.  And so the female birds have absolute say in deciding who will and will not fool around.  The females visit large numbers of males and decline most of their overtures.  Why should she settle for anything less than the absolute sexiest gentleman in the forest?  She’ll find him eventually, and since he never helps any of his children’s mothers with child-rearing, she knows he’ll be available.

Male smooth guardian frogs protect their fertilized eggs and young tadpoles.  Large choruses of females will surround and serenade each available male, hoping to sway his desire.  Since males do all the parenting, they are very selective.

That’s the usual system – you do the work, you get to choose.

It’s a nice idea.  After all, choice means the ensuing activity is consensual, and the opportunity to consent is sexy.

Unfortunately, in many species, others attempt to subvert mate choice.  You know – those ducks.  Orangutans.  Humans.

meanMyriam Gurba’s Mean is alternately comic and horrifying.  In a chapter titled “Omnipresence” (after the trauma, danger seems to be everywhere), Gurba writes:

A stranger chose me to rape.

There was no nepotism involved.

Basically, I got raped for real. (I’m being cheeky here.)

Stranger rape is like the Mona Lisa.

It’s exquisite, timeless, and archetypal.

It’s classic.  I can’t help but think of it as the Coca-Cola of sex crimes.


You never predict that rapists are lurking in the sun, sky, and trees.


In The Evolution of Beauty, Prum writes:

prumOf course, it has long been clear that sexual coercion and sexual violence are directly harmful to the well-being of female animals.  But the aesthetic perspective allows us to understand that sexual coercion also infringes upon their individual freedom of choice.  Once we recognize that coercion undermines individual sexual autonomy, we are led, inexorably, to the discovery that freedom of choice matters to animals. 

Sexual autonomy is not a mythical and poorly conceived legal concept invented by feminists and liberals.  Rather, sexual autonomy is an evolved feature of the societies of many sexual species.  As we have learned from ducks and other birds, when sexual autonomy is abridged or disrupted by coercion or violence, mate choice itself can provide the evolutionary leverage to assert and expand the freedom of choice.

Many of the trappings of human civilization exist solely to subvert mate choice.  Powerful males did not want human females to exercise sexual autonomy, because what if she picks someone else?  And so men made marriage, Biblical commandments against both adultery and thinking about adultery, and a propensity to murder (or, on contemporary U.S. playgrounds, heckle) loose women.

Human males wanted to control the flow of genetic information without doing the work of parenting.  Just like ducks, whose females evolved corkscrew-shaped vaginas because only those individuals with complicated genitalia could exercise free mate choice amidst generations of rape culture.

Rape culture isn’t specific to Homo sapiens, after all.  It’s a disease of any species in which those who don’t put in the work decide they ought to make choices for others – and nobody stops them.

(Humans do perpetrate more sexual violence than other species, especially violence against non-humans.  Interspecies sexual assault strikes most people as outlandish, unless it’s being done on our behalf.  Farms, puppy mills, and zoos are major assault factories.  We assent to forcible fertilization because it produces large-breasted chickens, cute puppies, and caged “wild” animals for our screaming children to ogle.)

Not all species rape.  In some, coalitions of females defend each other.  In others, males enforce fairness.  Those who believe in justice can punish interlopers, providing females with the right to choose.  Feminism isn’t the exclusive provenance of females.  Injustice hurts everyone, and anyone can feel aggrieved by it.

On violence against women (part three): rape, evolution, and the dangers of partial truths.

IMG_0430-0This is third in a series.  Read Part 1 and Part 2.

Were you sired by a jerk?  Don’t worry!  You can still be good!

I’m mostly familiar with two theories addressing the question, “Why do men rape?”  One comes from feminism, like the thesis put forward in Brownmiller’s Against Our Will: violence against women is intended to keep them from overstepping boundaries.  This theory, to me, doesn’t provide a great rationale for why specific individuals would be rapists, but seems compelling when viewed from the perspective of culture, i.e. rape culture flourishes to subjugate women.  The second theory is from evolutionary biology; the main gist is that because human females make larger contributions toward the success of offspring than males, females have the upper hand in choosing mating partners.  Therefore males who are would seem to be poor choices for mating (because they’re unattractive, or unintelligent, or otherwise would make poor genetic sires) have an incentive to rape because it’s the only way they can pass on their genes.

I tend to think this latter theory is hogwash.  But I’m pretty biased against evolutionary psychology in general.

One thing I appreciate about the evolutionary biology theory, though, is that it addresses the individual perpetrator.  Especially the idea that rapists are motivated by sexual desire.  What I think the feminist theory gets right is that rapists are aided and abetted by a culture interested in suppressing women, but I imagine individual rapists to derive pleasure from their violence.

The thing I’m unconvinced by is the idea that there is an evolutionary explanation for rape, that this propagation strategy has been sufficiently “successful” over enough generations to now have a significant genetic driver.

Which is important to think about, for a couple reasons.  Like, more studies are published all the time in support of the evolutionary biology rationale.  The latest is from Langstrom et al., “Sexual offending runs in families: A 37-year nationwide study.”  And the second reason why I think this is an important topic to think about is more pernicious.  Because if the evolutionary biology explanation isn’t correct, but we as a society allow the trappings of science to convince us that it is, then there’s less incentive to rectify all the cultural problems that I feel are the major culprits behind violence against women.  Like, if we believed the problem was simply encoded in some people’s genes, why work hard to fix it?

Honestly, I don’t know of any work, in any species, that’s provided compelling evidence for rape as an evolutionary strategy.  Which isn’t to say that the idea is bad; I’d be pretty surprised if there were no species that had evolved a split set of mating strategies including the options 1) be attractive or 2) rape.  Because there are several species wherein males seem to be genetically programed to follow one out of a possible menu of many mating strategies, and the aforementioned split is just as reasonable as a split between 1) appear masculine, control territory or 2) appear feminine, mate with females in secret while scuttling through another male’s territory.

And, I’d like to think that I shouldn’t have to state this, but the fact that a certain behavior occurs somewhere in nature, perpetrated by some species or other, is obviously not a reason why we shouldn’t consider it loathsome.  Child neglect, bullying, cannibalism, murder, etc., are all perfectly valid evolutionary strategies.  My point in writing this essay is simply this: I saw a new scientific study with that attention-grabbing headline about sexual aggression running in families.  I wanted to put their findings and methodology in context.

Rape as propagation strategy seems to be best studied in orangutans.  If you’ll excuse me a moment of anthropomorphism here, it sounds very crummy to be a female orangutan.  Males exist in two forms: as juveniles their faces are “unflanged,” and after reaching sexual maturity they can either remain unflanged or proceed through a unidirectional transition to become “flanged” males, with hemicircular outcroppings of flesh from their temples to their jowls.  As a flanged male, their faces look somewhat reminiscent of stingrays (apparently female orangutans think this is quite attractive), and they are asserting bad-ass-itude; once flanged, a male will have to fight for its territory.  The transition is only worth making, therefore, once a male orangutan feels that it could successfully fight the other nearby flanged males.

Females voluntarily mate with flanged males; they pick whomever suits their fancy when in estrus, he protects them and mates with them.  But flanged males seem not to care much about the wellbeing of females at other times.  When not in estrus, females are on their own, and while they’re foraging they might be raped by unflanged males.

This is the closest I’ve stumbled across to a clear evolutionary explanation of rape within a species.  Even here, though, there are caveats: as far as I know, any male could transition to the flanged type, and no one has documented sexual violence by the flanged males.  So it seems that any orangutan might grow up to be a rapist, as long as he’s living in a region where all the other males are bigger and burlier than he is.  I don’t think anyone has shown a correlation between genetic factors influencing male build and sexual aggressiveness.

In other words, they’re all bad, but those who are lucky enough to think they can get what they want without violence don’t resort to it.  Or, wait.  No.  Because the flanged males still have to bash each other’s heads in.  So I guess it’s, there’s a developmental switch between using violence against women to propagate, versus using violence against other men to win mates.

See why I thought it was silly to mention the caveat that just because something happens in nature doesn’t mean it’s good?

The only other evidence I stumbled across is from chimpanzees, like in Feldblum et al.’s study “Sexually coercive male chimpanzees sire more offspring.”  What they found wasn’t rape, however.  They found that it takes being a violent jerk full-time for a male to increase his rate of paternity; aggressive behavior only while females were in estrus was not enough.  And, sadly, because this means reproductive success driven simply by a personality trait — a full-time propensity for violence — rather than a particular mating strategy, this is something that’s much easier for evolution to enrich in a population.  Because evolution is a sloppy process; it can only take what’s already present and make more of it.  But if there are genes that confer a predilection toward being a violent jerk, and being a violent jerk helps a chimp have more chimplets, then, yeah, over many generations it’d be easy for those genes to become prevalent.

Of course, that last claim was not addressed in the Feldblum et al.’s study.  And it’s important.  To build an evolutionary argument, it’s not enough to find that a certain trait confers reproductive success; you also need to ascertain whether that trait can be passed on to children.

And that, in particular, is what Langstrom et al.’s study addresses, which is why I thought it was important enough to write about.  If, in humans, the tendency to rape runs in families, perhaps it could have a genetic component.

Not that it does, mind you.  Religious sect also runs in families.  Language use.  Voting record.  Countless aspects of culture.  And it’d be silly to claim that all of those are dictated by genetics instead of going with the more parsimonious explanation that there are genetic contributions toward the use of language in Homo sapiens and that language usage allows us to pass on bits of culture through a parallel but separate evolutionary process (which is the underlying principal behind Richard Dawkins’ coining the term “meme.”  Which he originally applied to long-lived ideas like particular religious precepts, not pictures of kittens with silly captions.  But his word, like all words, evolved).

So, especially with small effects like what Langstrom et al. observed (feel free to glance at this editorial about the research to get a sense of why a “Five Fold Increase!” isn’t as meaningful as it sounds when the absolute numbers are very low), I’d worry that the issue is simply that growing up in a culture conducive toward violence against women might sway someone toward perpetrating further violence.  No genes necessary.  They did attempt to control for this by computing genetic relatedness for sets of children raised together, but I find it hard to imagine that half-siblings, for instance, could be expected to receive near-identical environmental exposure.  Which makes me predisposed to discount their findings.  Somewhat unfair, I know; except with retrospective data analysis, how could anyone test something like this?

Well, maybe we can’t.  I mean, honestly, we still don’t even know what  people should eat in order to be healthy.  (Click away.)

Or you might imagine that, even if there is a genetic predisposition toward sexual violence, that it could be explained away by postulating a genetic contribution to impulse control.  Perhaps that is the simplest explanation for Langstrom et al.’s results, since nearly half of their sample set of convicted sex offenders were also convicted of other non-sexual violent crimes.

Still, despite my qualms about this research, I wanted to write about it.  Because, whether correct or not, the publication of results like this can change our world.  If we convince men that they’ve evolved to be sexually aggressive, or that sexual aggression is a biologically reasonable response to cultural constructs in which they are relatively powerless in terms of attracting partners, we make it that much more likely that these bad behaviors will continue.  If we convince women that this is simply how men are, they’re much more likely to tolerate malignancy (consider that amongst victims of assault, a quarter have subsequent sexual relations with their assailants).

And, sure, if you trawl the literature you can find studies that claim the promulgation of these theories won’t make violence against women more common, but there is a big difference between a university student soberly contemplating a fictional scenario and actually behaving badly while drunk and at a party.  To me, it’s still an open question (to which I’m inclined to answer “yes”) whether believing that they’re genetically predisposed toward evil makes people more inclined to do evil.

Which leaves me with a conflict.  As a scientist, I care about truth.  I want people to know about our world.  But then, what should we do if the very act of spreading truth might make the world worse?

The whole truth wouldn’t — the idea that, sure, maybe your genes would have you do this, that, or the other thing, but even then, you still have a choice — but I honestly don’t know what to think about the risk of people learning only dangerous partial truths.