The Anatomy of Violence (34 page)

In case you are getting worried, other minor physical anomalies include adherent (attached) earlobes, electrostatic hair, and curved little fingers. It is believed that they may be caused by environmental teratogenic influences acting on the fetus, factors such as anoxia, bleeding, infection—or fetal exposure to alcohol.
⁴⁰
Don’t worry if like me you have only one or two minor physical anomalies—it’s having a handful that really counts.

Minor physical anomalies—like many other markers for violence—have not been systematically assessed in serial killers. But they have been systematically assessed in research studies on a wide variety of
antisocial populations of different ages, ranging from troublesome toddlers to violent adults. Beginning with a breakthrough paper in
Science
, minor physical anomalies have even been linked to peer
aggression as early as age three.
⁴¹
Again, in another study at the preschool level, more minor physical anomalies have been found in aggressive and impulsive boys.
⁴²
Moving on a little into elementary school, boys with problem behaviors have more anomalies.
⁴³
Transferring to secondary school and to the troublesome teens, minor physical anomalies in boys assessed at age fourteen predicted violent
delinquency at age seventeen. Interestingly, at this age, the relationship was specific to violent offending—it was not observed for nonviolent forms of delinquency.
⁴⁴
In this study the effects could not be attributed to potential confounds such as family adversity. At about the same age—but from a biosocial perspective—minor physical anomalies in seven-year-olds combined with environmental risk factors in predisposing the children to
conduct disorder at age seventeen.
⁴⁵
This
highlights again the biosocial key that we saw when we looked into birth complications—the interaction between a biological and a social factor in predisposing someone to antisocial behavior.

Minor physical anomalies assessed by pediatricians at age twelve predicted violent offending at age twenty-one by perpetrators now leaving
school and graduating on to violent criminal careers.
⁴⁶
Yet again, a biosocial interaction was observed with especially
high rates of violence found in those with both minor physical anomalies and a history of being raised in unstable home environments. As with birth complications, the presence of a negative psychosocial factor is required to trigger the biological risk factor in adults—and in both cases the effects are specific to violent offending.

It may seem bizarre. Some of
Lombroso’s ideas may seem very repugnant. Yet over a hundred years after his first theorizing, we can say that Lombroso was at least partially on the mark with his theory for Cain-like atavistic stigmata for criminal offending. We can also say—at least at a superficial level—that the book of
Genesis highlights for us external physical indicators of family feuds gone wrong. The key difference is that while the mark on Cain in Genesis was very visible, we never notice anyone’s minor physical anomalies. They are imperceptible without a close physical examination.

From a scientific standpoint we get another pointer to the fact that the seeds of violence are sown very early on in life—as early as the prenatal period.

How often do you look at your fingers? In all likelihood, not very often. But take a look right now at your right hand.
⁴⁷
With your palm facing you, look at the length of your fingers. Compare the length of the second digit with the length of the fourth digit. The second digit is your index finger, the fourth digit is your
ring finger. You’ll very likely see that the fourth digit is longer than the second. It is for most people, especially on the right hand. If you can compare yourself with someone of the opposite sex, see who has a longer ring finger relative to the index finger. Males in general have the advantage—they tend to have a longer ring finger compared with their index finger than women do. This
gender difference is also true in
baboons.

What causes this difference between the genders? Genetics is one explanation, with the same set of genes
⁴⁸
influencing both genitals and digit length.
⁴⁹
But in addition,
fetal
hormone exposure—in particular
androgens—plays a critical role. Sometime between ten and eighteen weeks of gestation there is a major surge in
testosterone production that among other things produces the primary gender differences we
see at birth. It not only masculinizes the nervous system and behavior, but it also influences the ratio of the length of the second to the fourth digit.
⁵⁰
The higher the testosterone exposure, the longer the size of the ring finger relative to the index finger. Hence men have a relatively longer ring finger than women.
⁵¹

The testosterone explanation of the digit difference seems relatively convincing. Several studies have observed that children with
congenital adrenal hyperplasia
⁵²
—a condition caused by high prenatal androgen exposure—shows this male effect of a relatively longer ring finger.
⁵³
Women who have larger waists relative to their hips often have higher testosterone levels, and such women have been found in turn to give birth to children with relatively longer ring fingers.
⁵⁴
Indeed, because assessing prenatal androgen levels is not easy, this finger difference has been touted as an indirect indicator of the level of androgens during fetal development.
⁵⁵

What do we know about people with a more male-like, longer ring finger? For one thing they tend to dominate, show physical advantages, have male-like characteristics, and have personalities linked to aggression. A study in Poland shows that females who have achieved elite status in athletics have relatively longer ring fingers compared with non-elite athletes.
⁵⁶
And such prowess is not restricted to the track or to Poland. Male British symphony orchestra musicians also have relatively longer ring fingers.
⁵⁷
On the field, English soccer players who are in the first team have longer ring fingers than those who are in the reserves.
⁵⁸
Some of you may recall the likes of Paul Gascoigne, Geoff Hurst, Stanley Matthews, Peter Shilton, Glenn Hoddle, Kenny Dalglish, and Ozzie Ardiles—soccer stars who represented their countries in international matches. These twenty-nine stars, as a group, were found to have longer ring fingers than a group of 275 professional footballers who had not played for their country. Furthermore, the more times they had represented their country, the longer their relative ring-finger length.

Another correlate of the long ring finger is
sensation-seeking and impulsivity
⁵⁹
—personality traits that we saw in the previous chapter to be linked to antisocial and violent behavior. People who are relatively
lacking in empathy also have longer index fingers,
⁶⁰
and antisocial, psychopathic offenders certainly lack empathy. Although the evidence is conflicting, men with a longer ring finger tend to have higher
attractiveness ratings.
⁶¹
Hyperactive children have a longer ring finger,
⁶²
and we know that there is comorbidity between
hyperactivity and conduct
disorder.
Gay men’s ring-finger lengths are often in between those of heterosexual men and heterosexual women.
⁶³
It’s not true of every study, but in a sense relatively longer ring fingers compared with index fingers go along with
male characteristics—high stimulation-seeking, low empathy, and hyperactivity.

Given this, it perhaps comes as no surprise that higher
aggression—a very male characteristic—is associated with longer ring fingers. In Canada, male undergraduates who are more physically aggressive have longer ring fingers,
⁶⁴
with the strength of this
relationship being as strong as the relationship between aggression and testosterone. In the
United States, male undergraduates with longer ring fingers report being both more aggressive and more likely to engage in male-related play activities.
⁶⁵
In
China we have been finding cross-cultural support for the relationship between high aggression and a longer ring finger in male but not female eleven-year-old schoolchildren.
⁶⁶

We often think of aggression in the domestic domain as a bit different from aggression toward strangers. Indeed, the field of
domestic
violence has been almost completely dominated by scientists with a strong social perspective on intimate partner violence. But relative ring finger length, with its status as a marker for prenatal testosterone levels, sticks up a rude finger gesture to this predominantly social view. Men with long ring fingers are more likely to use threats of aggression against their female romantic partners.
⁶⁷
They are also more physically violent toward them, and this is especially true for men whose female partners are cheating on them.
⁶⁸

By and large, the relative ring finger length relationship with physical aggression seems to be more true for men than for women. So what’s going on beneath the
Tarzan/Jane stereotypes of aggressive men and nurturing women? I think part of the answer is that women are just less aggressive than men, so aggression scores are more likely to bottom out in women. There is less variability in aggression to explain here. That is something we call a
floor effect, and it can suppress relationships. But more likely it’s because, as we saw in
chapter 1
, hard-core physical aggression is costly in an evolutionary sense. Women invest in their offspring more than men, and a woman who initiates violence is likely to be hit in return, which could be a danger to the survival of her offspring—more than would be true for the father of the child. So instead, more “softer” forms of aggression—like gossiping, rumormongering, making others feel guilty, and shutting others out of
relationships—are more in the female domain than full-blooded
physical aggression. Once we get down to assessing these softer forms of “relational”
aggression in women, studies do indeed find relationships between such behaviors in females and longer ring-finger lengths.
⁶⁹
They also show a relationship between finger ratios and more “
reactive aggression”—lashing out at others who have hurt or slighted them.
⁷⁰

And what about aggression in the
political arena? If you were the leader of a country and in conflict with your neighbor over diamond mines that had just been discovered in disputed territory, how would you react? Suppose you can either negotiate or go to war. Your choice is not entirely as free as you may think. It’s partly determined by your relative ring-finger length. Business-school students at
Harvard were placed in this game scenario.
⁷¹
The interesting parameter was the number of unprovoked attacks the leader would make on the neighboring country. As you might expect, men in general launched more unprovoked attacks than women—32 percent versus 14 percent. Let’s remember that by the tender age of one year, boys are already throwing and hitting more than girls.
⁷²
But what’s more interesting is that the students with longer ring fingers launched more unprovoked attacks, an effect that was as strong as the gender difference in aggression.
⁷³
If you are a Quaker, check out your political candidates’ finger lengths before casting your vote.

Why should this mark of
Cain—the longer ring finger than index finger—be a characteristic of aggressive individuals? Of course, the longer ring finger itself is not causing crime. It’s more that other factors that go into making a longer ring finger also go into making aggression. We have just seen how higher
testosterone in utero is responsible for the digit difference. In
chapter 4
we also saw how high testosterone is causally related to aggression. So perhaps we have it here—the longer ring finger is caused by high prenatal testosterone, which in turn fuels aggression. That higher surge in testosterone early in fetal development shapes a more prototypical male brain, which shapes more prototypical male behaviors, including sensation-seeking, interest in
sports, low empathy,
dominance, and, of course, aggression.

But is there something missing here, a question that begs to be answered? What causes higher testosterone exposure in utero?
Smoking cigarettes during
pregnancy can result in higher prenatal-testosterone exposure to the fetus that leaves its mark on finger length. We suspect this because mothers who smoke have higher testosterone levels,
and this can in turn reduce
estrogen exposure to the fetus, resulting in higher fetal testosterone levels. Experimental work in animals has shown a causal connection, with exposure to nicotine in the prenatal period resulting in higher testosterone in the fetuses.
⁷⁴
Given these links, it’s not too surprising that mothers who
smoke during pregnancy have male offspring with longer ring fingers than mothers who do not smoke.
⁷⁵

There is something elegant in this line of research. Unlike
brain-imaging research, where we can observe structural and functional changes to the brain that may be caused by violence and subsequent head injury, the digit difference precedes even the very initial development of antisocial, aggressive, and violent behavior. How do we know that for sure?
Ultrasound can give us images of fetuses, but it’s not possible to assess finger-length differences from such images. However, researchers in Turkey examined 161 fetuses that had been aborted at different stages of pregnancy and made exact measurements of finger lengths. They established that the gender difference was present by the end of the third month of gestation.
⁷⁶
There really does seem to be a process in place very early on in life that contributes to aggression many years later.