The Anatomy of Violence (5 page)

From our perspective on the evolution of violence, however, the most interesting element of the Yanomamo is what happens to
unokais
, the men who kill. They have an average of 1.63 wives compared with 0.63 wives of men who do not kill. The
unokais
have an average of 4.91 children compared with an average of 1.59 children for non-killers. In terms of
reproductive fitness, serious violence pays handsomely in two critical resources. First, lots of kids. Second, lots of wives to look after them. We can see how planned violence and the
lack of remorse over killing others have been rewarded in the
unokais’
society. These are precisely the features of Western psychopaths,
¹⁷
who also commit more aggressive acts than non-psychopaths, and are more likely to commit homicide for gain.
¹⁸

Inevitably, Western society does not condone such violence. We hardly applaud and reward people who kill others. Or do we? With significant pomp and ceremony we decorate and reward soldiers who have taken significant risks to kill others in warfare. Crowds cheer wildly as
boxers punch each other senseless in a
sport that we know results in
brain damage. We certainly revel in kung fu
movies or other film genres when the good guy beats the living daylights out of the bad guy.

Whatever our cultivated minds may publicly say about the senselessness of warfare, do not our primitive hearts still thrill to the drums of combat? Is this why we enjoy sports competitions, to watch the dominant winner end up on top? Is that what gives us the vicarious thrill and excitement of seeing someone win a gold medal at the Olympics? Or when a
violent tackle occurs in a football game? Our present-day cultured minds weave an alternative story to explain the feeling—we just love sports, that’s all. But why? Isn’t it because selection pressures have built into us a mechanism to carefully observe who ranks where, empathic skills to imagine ourselves as a winner, basking in that reflected glory, giving us that “feel-good” mood and a desire to emulate such achievements?

Mundurucú women are clearly attracted to men around them who kill. Have you ever wondered why seemingly sensible, peaceful women want to marry serial killers in
prison? Their primitive heartstrings are being plucked by the siren’s call of the serial-killer status. They yearn to be with a strong male, even when their modern minds might logically object. At a milder level we have a morbid fascination with true crime. Something attracts us to violence. That evolutionary pull may even have explained why you bought this book.

Part of the
attraction we have to violence is that when executed in the right place and the right time, it’s
adaptive—even today. The vestiges of our evolutionary backgrounds persist, far more than we care to imagine. Let’s take this a step further into the here and the now to examine in what specific situations aggression is adaptive, and what aspects of crime can be explained from an evolutionary perspective.

I mentioned earlier that people in general are a hundred times more likely to be killed on the day they are born than on any other day.
¹⁹
Murders of children and adolescents are most likely to occur in the first year of life.
²⁰
And within that year, eighteen times more children are murdered on the day they were born than on any other day.
²¹
In 95 percent of these cases, the babies were not born in a hospital. They are mostly the product of undesired,
unplanned pregnancies. They are battered
to death (32.9 percent), physically assaulted (28.1 percent), drowned (4.3 percent), burned (2.3 percent), stabbed (2.1 percent), or shot (3.0 percent).
²²
It all flies in the face of the exhilaration that most couples experience on the day of their child’s birth. But an explanation for this seeming contradiction can be found within the layers of evolutionary psychology theory.

Indeed, once we step across the threshold of the home, there are facts that seem to fly in the face of an evolutionary perspective on violence. For example, people are more likely to be killed in their home by a family member than by a stranger. How can that make sense from an evolutionary standpoint? Don’t we expect solid protection of everyone at home to ensure that the family’s
genes are passed on to future generations?
Martin Daly and
Margo Wilson are two Canadian evolutionary psychologists who have done more than anyone else to resolve enigmas like this and to further demonstrate the power of an evolutionary psychological perspective on violence.

What they demonstrated was an inverse relationship between the degree of
genetic relatedness and being a victim of homicide. So the less genetically related two individuals are, the more likely it is that a homicide will take place. For example, in Miami, 10 percent of all homicides were the killings of a
spouse—a family killing—but of course, spouses are almost always genetically unrelated. In fact, Daly and Wilson found that the offender and the victim are genetically related in only 1.8 percent of all homicides of all forms.
²³
So 98 percent of all homicides are killings of people who do not share their killer’s genes.

Selfish genes in their strivings for immortality wish to increase—not decrease—their representation in the next gene pool. Hence this inverse relationship between genetic relatedness and homicide. On the other hand, if you are living with someone not genetically related to you, you are eleven times more likely to be killed by that unrelated person than by someone genetically related to you.

Stepparents are a particularly pernicious case in hand, a fact captured in countless myths and
fairy tales. Remember the grim story of
Hansel and Gretel, whose wicked stepmother badgered their natural father into leaving his children deep in the woods to die of starvation? Or
Sleeping Beauty’s evil and vain stepmother, who ordered a hunter to take her into the woods and slaughter her? Recall
Cinderella’s cruel stepmother? Actually, the reality is so potent that our childhood lives
are full of images of mean stepmothers—real or imaginary—almost as an eerie warning call for us to be on our guard.

Did you grow up as a child with a
stepparent? If you did and you survived unscathed, you’ve done pretty well. In England, only 1 percent of babies live with a stepparent,
²⁴
and yet 53 percent of all baby killings are perpetrated by a stepparent.
²⁵
Data from the United States show a similar pattern—a child is a hundred times more likely to be killed as a result of abuse by a stepparent than by a genetically related parent. If we look at child abuse, we see the same thing. Stepparents are six times more likely to abuse their genetically unrelated child under the age of two than genetic parents.

It’s a finding that makes you wonder if in cases of death from abuse by someone thought to be the biological parent, that person may not be the genetic parent after all. In cases where the children and the father believe that they are genetically related, it is estimated that in about 10 percent of cases the father is not the genetic father. Could at some subconscious, evolutionary level the father sense genetic unrelatedness and pick on the unrelated child? Such abuse would be a paternal strategy to push that child out, to minimize the resources given to him, and instead maximize resources for other, genetically related children. We know that stepparents sometimes selectively abuse their stepchildren, sparing the children in the family who are genetically related to them.
²⁶

Such actions of some stepparents can thus be comprehensible from an evolutionary perspective. But more perplexing are parents who kill children they
are
genetically related to. How can evolutionary theory come to grips with these killings?

The basic concept to remember here, if you think back to your own parents when you were growing up, is that they likely worked hard to raise you—and don’t they just let you know it sometimes! They worked their fingers to the bone and sacrificed much for your future betterment. Okay, so that’s par for the course when it comes to looking after your own genes. But also bear in mind that the longer a child lives, the more her parents invest in her. But suppose someone’s genetic parents change their minds about their
investment? If they do, they ought to do it early on before they waste more energy. And that’s exactly what we see.

Take a look at the top graph in
Figure 1.2
, showing the age at which a child will be killed by its mother
if
she is indeed going to kill it. It shows homicides per million children per year averaged over a period from 1974 to 1983 in Canada. You’ll see that the peak age for killing is in
the very first few months of that little baby’s life.
²⁷
After that time, the homicide rate drops dramatically and keeps on declining right throughout adolescence. Soon after birth the mother bails out on her own baby. Maybe she wants to move on. Maybe her mate has moved out and she knows she’s better off without this baggage, better able to attract a new mate. Whatever the reason, there is a strong age effect to be explained.

Figure 1.2
   Age at which Canadian children are
murdered by their mother, father, and others

I think I know what you’re thinking. Some mothers just after birth have
puerperal psychosis. They sink into a very deep depression with
psychotic features, and amid their despair and madness they may kill their kid. Fair point, because this condition does affect about one in a thousand mothers after birth. But the response lies in data shown in the middle graph of
Figure 1.2
. You can see exactly the same infanticide age curve for
fathers.
²⁸
If they are going to kill, it’s again in the very first year of life, when their
investment is minimal. Fathers don’t give birth and so they don’t suffer from puerperal psychosis. Consequently, this form of psychosis cannot explain the maternal data in
Figure 1.2
.

Maybe it’s all that screaming and sleeplessness that comes in the first year that drives the parents to kill their offspring. It’s not a bad explanation. But tell me, if you have ever had a child, what was the worst year—that first year when they were innocently crying, or the teenage years, when they were yelling in your face? Or, if you haven’t had kids, at what age do you think you were hardest on your mother and father? I’d go for the teenage years any day, and yet look at the rate at which parents kill their teenagers—that’s strangely when children are least likely to get killed by them. But if you are a teenager don’t push your luck with your parents, as a few do get killed.

Don’t push your luck with anyone else either. You’ll see from the bottom chart in
Figure 1.2
that when we look at the killings of kids by
nonparents
, rates are low early on but shoot up in the teenage years. Why? Because that’s the age when renegade youths are cruising the streets looking for fun and meeting up with strangers. It’s also when children are less closely supervised by their parents and when risk-taking is highest.

There are other environmental triggers that from an evolutionary perspective help explain why parents might kill their young offspring. A baby may be born with a congenital abnormality that reduces the odds of survival or reproduction, or it may have a chronic illness that saps parental resources. Even with normal offspring, if food is short it may pay the parents in terms of genetic investment to spend scarce resources on the survival of an older sibling closer to the age of maturity and independence, rather than spreading the butter too thinly, trying to support both the newborn and the older sib.

Even if there is no older sibling, killing the baby could make evolutionary sense. In some
bird species where both parents forage for their offspring, the death of one parent can result in the other parent abandoning the offspring. The load is just too hard to bear, and it’s better for the remaining parent to look after number one and try again
in the reproductive success game. Don’t we sometimes get a sense of that in stories of young
mothers abandoning their babies? We tend to interpret their actions as due to social processes like immaturity, shame, or teenage impulsivity. Shame may be the superficial explanation, but at a deeper level the underlying cause may be cold-blooded maximization of reproductive success. The negative emotions and behaviors that we attribute to the mother in trying to explain the homicide may not be the whole story. The
selfish genes inside the teenage killer mom may be the ultimate source of such callous, cold-blooded behavior.