by Adrian Raine
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 infidelity43 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.
MEN ARE WARRIORS, WOMEN ARE WORRIERS
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.
The simple evolutionary explanation is that women are worth fighting for. They are the valuable resource that men want to get their hands on. Women bear the children, worry about their health, and make up the bulk of the parental investment. This is also true throughout the animal kingdom. Where one sex provides the greater parental investment, the other sex will fight to access that resource. Evolutionary theory argues that poorer people kill because they are lacking resources, an argument shared in common with sociological perspectives. And the reason men are overwhelmingly the victims of homicide is because men are in competition with other men over those resources. Men who murder are also about twice as likely to be unmarried as non-murdering men of the same age.50 They have a greater need to get in on the reproductive act, and are willing to take warrior risks. For men one of the underlying causal currents for violence is competition for resources and difficulties in attracting females into a long-term relationship.
Let’s also not forget warrior men in the home context. Violence can be used to dominate, control, and deter a potentially unfaithful spouse. Just as lions who take over a female from another male will kill the young and inseminate the lioness, aggression toward stepchildren is a strategic way of motivating the unwanted brood to move on and not take up resources needed for the next generation bred by the stepfather.51
Consider also that sex differences in aggression are in place as early as seventeen months of age.52 Boys are toddler warriors. This might be expected from an evolutionary perspective that says males need to be more innately wired for physical aggression than females, to prepare them for later combat for resources. Seventeen months is a bit too young for sex differences to be explained in terms of socialization differences. Social-learning theories of why males are more aggressive run into trouble with the fact that the gender difference in aggression, which is in place very early on, does not change throughout childhood and adolescence.53 Socialization theory would instead expect sex differences to increase throughout childhood, with increased exposure to aggressive role models, the media, and parenting influences, but they do not. Consider also that violence increases throughout the teenage years to peak at age nineteen. This is consistent with the notion that aggression and violence are tied to sexual selection and competition for mates, processes that peak at approximately this age.54
While male warriors perpetrate most violent offending, females can be aggressive too, in a surreptitious sort of way. On balance, however, women tend to be worriers rather than warriors for reasons that evolutionary psychology can explain.
Women have to be very careful in their use of aggression and sensitive in their perception of it because personal survival is more critical to women than to men. That’s because they bear the brunt of child care and their survival is critical to the survival of their offspring. In unison with this standpoint, laboratory studies show that women consistently rate the dangerousness of an aggressive, provocative encounter higher than men do.55 Women are also more fearful than men of situations and contexts that can involve bodily injury.56 They are more likely to develop phobias
of animals and medical and dental procedures. While they are more averse to physically risky forms of sensation-seeking, they are not averse to seeking forms of stimulation that do not involve physical risk—things like novel experiences through music, art, and travel.57 Women also have a much greater concern over health issues than men. They rate health as more important and also go to the doctor more often.58
Fearfulness of bodily and health injury is therefore the psychological mechanism that evolution has built into women to protect them from death, helping to ensure the survival of their young. Thus, the fact that women are far less physically aggressive than males, in almost all arenas in life and in all cultures across the world, can be explained by an evolutionary principle.59 Women are more averse to physical aggression than men because of its reproductive impact. Yet what would happen if we lowered the risk of bodily injury from aggression?
In this case a different scenario gets played out. John Archer, of the University of Central Lancashire, has documented that the sex difference in aggression is highest at the most severe levels of physical aggression, is much lower when it comes to verbal aggression, and is negligible with “indirect aggression.”60 Essentially, females are much more likely to engage in aggression when the cost to them in terms of physical injury is minimal. Indeed, Nicki Crick, at the University of Minnesota, has argued that females are more likely than males to engage in this “indirect” or “relational aggression,” which takes the form of excluding others from social relationships and group activities and damaging their reputation in their peer groups—gossiping, spreading rumors, humiliating the individual. Ladies, do you recall this from your teenage days or experience it now in your current working life?
So rather than being physically violent, women take a more passive-aggressive strategy. They compete in terms of physical attractiveness—the quality most desired by men, who use it as a guide to fertility—and allow access to the man with the most resources. David Buss argues that women are much more likely to call their competitors ugly, make fun of their appearance, and comment on their fat thighs.61 Women attempt to ruin their rivals’ reputation by saying they have a lot of boyfriends, sleep around a lot, and are sexually promiscuous.62 Men don’t like hearing that from an evolutionary standpoint because if they get together with such a woman, they may end up rearing some other man’s offspring. Consequently, such slanderous gossiping is an effective verbal-aggression strategy for women to use that does not run a high risk of physical harm.
We’ve seen here how violence and aggression is based partly on primeval evolutionary forces from the past. While reciprocal altruism can rule the day, antisocial cheating can also be a successful reproductive strategy, especially when psychopathic cheats migrate from one population to another. I’ve tried to illustrate how stealing, rape, homicide, infanticide, spousal abuse, and spouse killing can all be viewed from an evolutionary perspective. We’ve also seen anthropological examples of how different ecological settings could have given rise to either cheating or reciprocal altruist reproductive strategies. Males have evolved to use physical aggression to increase genetic fitness, while women have evolved to be concerned over their own health and that of their progeny, resorting to a safer form of relational aggression to protect their genetic interests. While evolutionary theory cannot, by any means, explain all violence, it at least provides us with a broad conceptual base with some degree of explanatory power.
The seeds of sin are rooted in our evolutionary past, the time when hominids formed social groups that shaped norms for helping behaviors—norms that a minority could break. Genes are the name of the evolutionary game, and therein lies an important implication for us. Talk about evolution, and by necessity we invoke genes. I’ve argued that antisocial, psychopathic behavior has evolved in some of us as a stable evolutionary strategy. In this ruthless, selfish context, rape is viewed not simply as a mechanism by which men exert power and control over women, as many feminists would argue. It is also the ultimate evolutionary cheating strategy—“love” them and leave them. Inseminate as many women as you can, then leave them to get on with the hard work of raising Cain and reproducing your bad genes. So the next step we will take in tracing the anatomy of violence is to understand the genetic basis to brutishness, and which individual genes stand out as our “usual” suspects.
2.
SEEDS OF SIN
The Genetic Basis to Crime
Jeffrey Landrigan never knew his father. He was born on March 17, 1962, to a mother who abandoned him at a day-care center when he was just eight months old. But little Landrigan got lucky. He was adopted into an all-American family in Oklahoma. His adoptive father was a geologist named Nick Landrigan, whose wife, Dot, was a doting mother to both Jeffrey and their biological daughter, Shannon. Well-educated, straight-laced, and respectable, they provided a perfect new beginning for little Jeffrey.
Yet an insidious shadow from the past was cast over this baby that was to effectively seal his fate. By the age of two he was already throwing temper tantrums and displaying emotional dyscontrol that quickly escalated. He began abusing alcohol at the age of ten. His first arrest came when he was eleven, after he burglarized a home and attempted to break open the safe. He skipped school, abused drugs, stole cars, and spent time in detention centers. He was moving rapidly into his criminal career. When he turned twenty he had a drinking bout with a childhood friend who wanted Jeffrey to be the godfather of his soon-to-be child. Jeffrey’s response? He stabbed his friend to death outside his friend’s trailer. In 1982 he started a twenty-year sentence for second-degree murder.
Incredibly, Landrigan escaped from prison, on November 11, 1989, and headed out to Phoenix, Arizona. It could have been a new life and a clean sheet, yet murder seemed almost destiny for Landrigan. In a Burger King in Phoenix he struck up a conversation with Chester Dyer. Dyer was later found stabbed and strangled to death with an electrical cord, with lacerations on his face and back. Pornographic playing cards were strewn around the bed, with the ace of hearts propped up maliciously on the victim’s back. But Landrigan’s luck was running out. While exiting the apartment he left his footprint in sugar on the floor. He was consequently arrested, found guilty of homicide, and sentenced to death.
This might have been the last chapter in Landrigan’s dramatic, topsy-turvy life. But the strangest twist was yet to come. While Landrigan was on death row in Arizona, another inmate told him of a man named Darrel Hill, a con he had met while on death row in Arkansas. Darrel Hill was Jeffrey’s spitting image. Hill turned out to be the biological father that Jeffrey Landrigan had never seen. He was a dead ringer for Landrigan, and looks were not the only eerie similarity.
Darrel Hill had himself started his criminal career at an early age. He too was a drug addict. Like Landrigan he had killed not once but twice. He too had escaped from prison. Landrigan had clearly inherited much more than his father’s looks. They could hardly have been more similar.
And that’s not all. Jeffrey Landrigan’s grandfather—Darrel Hill’s father—was also an institutionalized criminal, who was shot to death by police after he robbed a drug store in a high-speed chase in 1961. He died just feet away from his then twenty-one-year-old son Darrel.
What do we make of this? Perhaps Darrel Hill summed it up best when he said:
It don’t take anyone too smart to look at three generations of outlaws and see there’s a link of some kind, there’s a pattern.1
Is there a “killer gene”? Or if not one, then multiple genes that, either on their own or in an intricate conspiracy with the environment, shape killers like Hill and Landrigan? Jeffrey Landrigan was adopted and raised in a safe and nurturing environment, yet despite all the love that his parents gave him—he could not be salvaged. This fascinating natural experiment—in which a baby with a violent heritage was transferred from a life of poverty and squalor into a loving, caring, successful family, yet still became a killer—suggests that there really is a genetic predisposition to
violence.
Criminologists for decades have strongly resisted this idea. In this chapter I’m going to not just try to persuade you beyond a reasonable doubt, but also explain why social scientists are also opening up their minds to this fascinating and important perspective. To begin with, we’ll delve into results from adoption studies that systematically examine cases similar to Landrigan’s. In these studies, babies whose biological fathers were criminals were adopted away into noncriminal homes. We’ll see that such babies were much more likely to become adult criminals than were babies who were also adopted but whose biological fathers were not criminals.
A second research design that uses identical and fraternal twins renders the same conclusion. Identical twins, who by definition have all of their genes in common, are much more similar to each other on crime and aggression than fraternal twins, who have only 50 percent of their genes in common.