The Anatomy of Violence (6 page)

Figure 1.3
   Age of mother when she kills her own child

There’s one more point to make about parents killing their children: how old the mother is when she kills her own child. The upper graph of
Figure 1.3
shows the rate of child homicides as a function of the mother’s age among the
Ayoreo Indians of
South America. It’s highest when the mother is under the age of twenty, and it goes down after that. Why would that be? The mother is more fertile when she’s younger—and more attractive in drawing a desirable mate to her. The older she is, the more it makes sense to hold on to her long-term
genetic
investment because it’s harder to make up the loss at this later point in her reproductive life.

And it’s not just the Ayoreo Indian mothers who kill at an early age. If you look at
Canadians in the lower half of
Figure 1.3
, you’ll see the same age-to-murder curve.
²⁹
Your mother is much more likely to kill you when she is still young. Being young, her reproductive years lie ahead of her and she has more options. Perhaps the current biological father has abandoned her. Perhaps she has a new suitor who can promise her more. Either way, the selfish gene ticking away inside her signals that it’s time to dump her baggage and go on vacation looking for a new mate.

Put all of this together, and what comes across is that genetic relatedness, fitness, and
parental investment are intriguing reasons for why adults kill their kids. Patterns of homicide can indeed be clarified by the application of sociobiological principles. Of course there are other processes that help explain why a parent kills his or her child—it’s not just the selfish gene at work. Yet whether we are aware of it or not in the twenty-first century, the machinations of deep evolutionary forces are laboring away down in the depths of our humanity, forging devious tools to maximize our genetic potential. And behind those closed doors in the family home, those forces don’t end with killing your kids.

Is
rape an act of hate? A malicious and derisory act against women condoned by a patriarchal society where men attempt to control and regulate their womenfolk? Or can this act of violence be partly explained by evolutionary psychology?

We can view the rape of a nonrelative as the ultimate genetic
cheating strategy. Rather than striving to accrue resources to attract a female and investing years in the upbringing of their
offspring, a male can cut through this tedious process in the twinkling of an eye. He just needs to rape a woman. Men have hundreds of millions of sperm that are always at the ready to inseminate a woman. The sex act is quick. And the male can immediately walk away, never to see that woman again. He knows that if pregnancy does occur, there is a decent chance that the female will care for their joint progeny. His selfish genes have reproduced.

How often will a rape result in a pregnancy? This was estimated in one study of 405 women aged twelve to forty-five who had suffered
penile-vaginal rape. The total base rate was 6.42 percent, which was twice as high as the 3.1 percent base rate for unprotected penile-vaginal intercourse in consensual couples. After correction for the use of
contraceptives, the pregnancy base rate from rapes was estimated at 7.98 percent.
³⁰
The rates of pregnancies from rape can only be estimates because paternity is not investigated with definitive DNA evidence. Some women could “invent” a rape as a cover-up for an
unwanted pregnancy. However, other studies have also reported higher rape-pregnancy rates than consensual-sex-pregnancy rates. It is nevertheless surprising. If we accept the findings, why would rape be more likely to result in a pregnancy?

One
conceivable hypothesis is that rapists are more likely to inseminate fertile women. Rapists select their victims, and we certainly know that they are far more likely to select women at their peak reproductive age than other women.
³¹
Furthermore, putting age aside, the possibility that a rapist may be more visibly drawn to women who are the most fertile is not impossible. Females with a smaller waist relative to their hips are viewed as more
attractive in many cultures throughout the world. This smaller
waist-to-hip ratio is also associated with increased
fertility as well as better health.
³²
Consequently, male rapists could in theory select a more fertile female, consciously or subconsciously, based on how she looks.

Not all rapists choose victims they find attractive. It can even be the other way around. When I worked with prisoners in England, one rapist told me that he specifically picked out
unattractive
women to rape. Why would he do this? His argument was that an unattractive woman does not get enough sex, so it’s okay to give her the sex that she really wants. This is just one example of a number of cognitive distortions that some rapists have.
³³
Their perverted belief is that women actually enjoy the act of rape and interpret it as the experience of a lifetime—their ultimate sexual fantasy coming true.

Ideas like this may be inadvertently fueled by the fact that some women when raped actually achieve
orgasm, even though they may strongly resist and are traumatized by the attack.
³⁴
True prevalence data are hard to come by because rape victims understandably are embarrassed to admit that they achieved orgasm during such a disgraceful violation. Clinical reports place the rate of the victim experiencing orgasm at about 5 to 6 percent, but clinicians also report that they suspect the true rate to be higher. This may well be the case,
because research reports document that physiological arousal and lubrication occurs in 21 percent of all cases. Why would that happen? Because in half the cases, the date-raped woman was actually attracted to the perpetrator before the act. Orgasm and the associated contractions are thought to facilitate conception by contracting the cervix and rhythmically dipping it into the sperm pool. This admittedly has a modest effect, as sperm retention is increased by only approximately 5 percent with orgasm.

Clearly, conception does not require orgasm,
³⁵
so we cannot place too much weight on the physiological arousal of some women during rape as a prelude to pregnancy. Nevertheless, the fact remains that
rapists generally select their victims and appear to consciously or subconsciously select more fertile women. This selection strategy would explain the purported increased pregnancy rate in rape victims and can be viewed in an evolutionary context. If a man is going to take
risks raping a woman, the strategy would be to pick the fertile one and enhance one’s inclusive
fitness.

There are, of course, risks associated with this particular
cheating strategy. The male could suffer physical injury. Worse, he could be detected and beaten. Throughout much of human history rapists have been alienated or killed. In modern times he would be thrown into prison alongside psychopaths and murderers, where as a
sex
offender he is at high risk for being beaten and raped himself. So evolutionary theory argues that there is a subconscious cost-benefit analysis at work—weighing the potential costs resulting from detection against the benefits of producing a child. Dominant men with resources can already attract mates, so one might expect that the cost-benefit analysis might tip the scales in favor of rape when the perpetrator has relatively fewer resources. In support of this prediction, rapists are indeed more likely than non-rapists to have lower socioeconomic status, to leave school at an earlier age, and to have
unstable job histories in unskilled occupations.
³⁶

We can question evolutionary theory because it can be too all-encompassing; we cannot take it too far in explaining
violence. Drug cartels in
Colombia and the
availability of hand
guns in the United States contribute significantly to explaining why these countries today have high homicide rates, and yet these influences lie outside the domain of evolutionary theory. I think you would admit that an evolutionary perspective can help explain facts about rape in quite a compelling way.
While women of any
age can be raped, we’ve noted that men are much more likely to rape women of reproductive age.
³⁷
Interestingly, women of reproductive age who are raped experience more extreme psychological pain than younger or older women. This has been interpreted as an evolutionary learning mechanism that focuses these women’s attention on avoiding contexts where they could be raped and have their overall reproductive success reduced.
³⁸
At another level, we know that men find it far easier than women to have sex without concomitant emotional involvement. Why? Because they do not need to hang around after the sex act is over. In contrast, from an evolutionary perspective, women need a long-term commitment from their
male mate to help rear any child that might result from their union, and so they have more need of an emotional, personal relationship. Finally, men very rarely kill the women they rape; although they have the potential to kill, they want their offspring to survive.

But what about rapes that occur between partners in a marriage or other long-term relationship? Between 10 percent and 26 percent of women report being raped during their marriage.
³⁹
How can this be viewed through evolutionary lenses?

A great deal of research has documented that both physical and
sexual violence perpetrated by men in a relationship is fueled by sexual
jealousy.
⁴⁰
Infidelity is very distressing for both males and females, but men and women differ in terms of what causes these distressing feelings. Jealousy is the primary motive for a husband to kill his wife in 24 percent of cases, compared with only 7.7 percent of cases in which the wife kills her husband.
⁴¹

Think about this yourself in your own life. Imagine that you are deeply involved in a serious romantic relationship. Now you discover that your partner has become very interested in somebody else. Now imagine two different scenarios. In the first, your partner has a deep emotional—but not sexual—relationship with the other person. In the second scenario imagine that your partner has enjoyed a sexual—but not emotional—relationship with the other person. Which one of these scenarios would upset you most?

David Buss, of the University of Texas at Austin, who conducted research into this question, found that men were twice as likely to find the second scenario the most upsetting—it’s the sexual relationship that bothers them, not the emotional relationship. While men find the sexual infidelity most distressing, women in contrast find the
emotional infidelity most distressing. These sex differences were still true for scenarios where both forms of infidelity occurred. These findings on Americans also hold true in
South Korea,
Japan,
Germany, and the
Netherlands.
⁴²
Men and women in different cultures differ in just the same way. Relatedly, men have been reported to be better than women in their ability to detect infidelity
⁴³
and are more likely to simply suspect infidelity in their female spouses.
⁴⁴

What can explain the replicable sex difference in the green-eyed monster of jealousy? The explanation is that men are more distressed about infidelity because they could end up wasting resources and energy in raising a child genetically unrelated to them. Women, on the other hand, are concerned about infidelity because it means they may lose the protection, emotional support, and tangible resources provided by their partner. In both cases, resources are again the driving force behind our intense emotional feelings, but in subtly different ways.

These findings on jealousy now render for us a perspective on why male
sexual jealousy can fuel so much
physical and sexual aggression in partner relationships. Men who force sex on their spouses are found to have higher levels of sexual jealousy than men who do not.
⁴⁵
Men may use violence as a mechanism to deter future defection by their female partner.
⁴⁶
A woman will think twice about having another dangerous liaison if it results in her being battered nearly to death.

Yet this gives us even more food for thought at the evolutionary dining table, where resources and reproduction are the vittles. Why would a male partner rape his female partner in response to an infidelity? You might say it’s simply an act of revenge. But lurking under the surface of this social argument may be a deep-rooted evolutionary battle that influences violence and crime—
sperm wars.

If a woman did have sex with another man, from an evolutionary standpoint her partner will want to inseminate her as quickly as possible. His sperm will then compete with sperm from the unknown rival in a battle to access the woman’s egg. Furthermore, by getting his sperm into her reproductive tract at regular intervals during a potentially prolonged period of suspected sexual infidelity, he puts off the chance that any foreign sperm will be successful in getting to that prized egg. At regular intervals he can top off his sperm in her cervix by injecting 300 million warriors. Half of these will end up in a flow-back that comes out of the vagina and onto the bed sheets, while the rest
have further work to do, beginning their arduous journey for the next few days toward the egg in competition with someone else’s sperm.
⁴⁷

In the
genetic
cheating game there’s no stopping
men.
Women certainly have a hard time of it. They get raped by strangers. They get raped by friends. They get raped by their partners. Yet women are not always the victims. We’ll see that they have their own subtle and conniving ways of waging war to promote their
selfish genetic interests.

Let’s start with men
as warriors. We all know that men are more violent than women. It’s true across all our human cultures, in every part of the world. The Yanomamo are not the only group whose men gather together to conduct killings in other villages. There has never in the history of humankind been
one example
of women banding together to wage war on another society to gain territory, resources, or power.
⁴⁸
Think about it. It is
always
men. There are about nine
male
murderers for every one female murderer. When it comes to same-sex homicides, data from twenty studies show that 97 percent of the perpetrators are male.
⁴⁹
Men are murderers.