The Dangerous Passion: Why Jealousy Is as Necessary as Love and Sex (8 page)

The design of the defense, in short, has three essential
components—input, decision rules, and output—whose nature must be revealed in
order to plumb the mystery of jealousy and its explosive manifestations. In subsequent
chapters we will explore this design in greater detail. For now, the presence
of a poignant defense mechanism implies something to defend against. And that
raises the next question: Given that marital vows promise devotion and fidelity
“until death do you part,” why do more than half of all married couples suffer
from an infidelity at some point in their marriages? Why are people tempted by
adultery in such great numbers, given that they risk losing so much? And how
does jealousy combat these threats?

Most professionals who devote their lives to studying the
mysteries of the human mind focus on a single topic or phenomenon. Among the
ranks of psychologists we find expert specialists in areas such as aggression,
cooperation, attitudes, status, love, language, the ear, the eye, panic
disorder, attention deficit disorder, and narcissistic personality disorder.
The human mind, however, does not exist in isolated bundles. It contains a
complex web of interconnected mechanisms. Furthermore, human minds cannot be
understood individually or in isolation. Our minds are designed to deal with
the minds of other humans.

One of the most important tools for understanding jealousy is
the theory of co-evolution—the reciprocal changes that occur sequentially in
interacting species or between the sexes within one species. Predators and prey
provide the clearest illustration of the theory of co-evolution. Rabbits are
natural prey for foxes, but the two species coexist in a special way. The rabbits
captured and eaten by foxes tend to be those who are slower, more preoccupied,
less observant, and less attentive to the hostile forces around them. The
quicker, more attentive rabbits survive and leave more descendants. Each
generation of rabbits, therefore, is slightly more adept at evading foxes than
the previous generation.

Now consider things from the foxes’ perspective. In each
generation, foxes who are more agile and fleet of foot are more successful at
catching rabbits. The uncoordinated and sluggish foxes fail to feed and leave
fewer descendants. So each generation of foxes is in some slight way better
equipped to catch rabbits. Each increment in the speed and agility of rabbits,
in essence, imposes selection pressure on foxes, just as each increment in the
speed and agility of foxes imposes selection pressure on rabbits. The changes
over time in rabbits and foxes, like all predators and prey, are best described
as a co-evolutionary spiral that continues indefinitely, or until natural
physical limits are reached.

The same logic applies to parasites and their hosts. Humans play
host to thousands of parasites that cannot exist without us. Parasites, as a
general rule, feed on the host organism, and can destroy it over time. Hosts
have evolved defense mechanisms to combat parasites, such as immune systems.
The parasites that survive, however, are those that are most skilled at evading
the host’s defense mechanisms. Parasites and hosts thus co-evolve in a
never-ending spiral, with each change in hosts imposing selection pressure on
parasites, and each change in parasites imposing selection pressure on the
hosts.

The logic of reciprocal changes in interacting species applies
with equal force to interacting sexes within a species. Consider as an example the
co-evolutionary spiral that occurs between men and women over the linked issues
of commitment and sex. As I documented in
The Evolution of Desire,
women have evolved a preference for partners who show reliable indications of
the ability and willingness to channel resources to them and their children.
Over human evolutionary history, women who succeeded in attracting committed
men survived and reproduced more successfully than women who failed to attract
such men.

Women’s preferences, in turn, can exert co-evolutionary
selection pressure on men. Men who display reliable cues to commitment are
preferentially chosen by women; men unable to display these cues get banished
from mating. Decisions to mate, however, are always made in a shroud of
uncertainty, which opens the door to deception. Some men may develop a strategy
of providing false cues to commitment, luring the woman into a sexual
encounter, and then abandoning her. Men’s deceptive strategy is one co-evolved
outcome of women’s initial preference for commitment.

As a strategy of deception spreads, however, it produces
selection pressure on women to screen out the deceivers. Women might begin to
insist on a longer period of courtship, for example, before consenting to sex,
or look for signs that the man is “playing the field,” such as how much his
attention is diverted from their conversation when an attractive woman walks
by. They might develop tests of a man’s commitment, such as asking that he
cancel watching the Monday night football game with his friends to attend to
her needs.

As women developed the ability to detect deception, they imposed
selection pressure on men to become better deceivers. And so the
co-evolutionary spiral continues, with each increment in one sex producing
reciprocal evolutionary change in the other. Adaptations in one sex lead to
counter-adaptations in the other, and those in turn lead to further
counter-adaptations and counter-counter-adaptations. As long as the strategies
of the sexes are in some degree of conflict, this co-evolutionary spiral will
continue unabated. At the current moment in time, we are poised in the middle
of this spiral, with women being excellent detectors of deception, as indicated
by factors such as their superiority over men in decoding nonverbal signals.
Men, in turn, can be notoriously skilled at deceiving women.

Jealousy provides the perfect example of the power of the
co-evolutionary spiral, and it starts with the evolution of love. Sustained
romantic bonds pose a special problem: how to defend against the possibility
that “poachers” lurk in the wings and might succeed in luring a partner away.
One popular song captured the essence of the poaching problem, albeit from a
man’s point of view: “When you’re in love with a beautiful woman, watch your
friends.” The more desirable your partner, the more intently interested
potential interlopers will be to intrude.

Jealousy evolved as a primary defense, a co-evolved response to
threats of a partner’s infidelity and abandonment. It becomes activated
whenever a person perceives signs of defection—a strange scent, a sudden change
in sexual behavior, a suspicious absence. It gets triggered when a partner
holds eye contact with someone else for a split second too long, or when a
rival stands a tad too close to your loved one or suddenly seems fascinated by
the minutiae of his or her life. These signals do not inevitably mean that a
partner will stray, just as the annoying blare of a fire alarm does not
inevitably mean that a fire is blazing. Alarms may be false. But these signals
alert us to the possibility of infidelity, since they have been statistically
linked with relationship loss over the long course of human evolutionary
history.

This is where co-evolution kicks in again. Jealousy, which gives
us sensitivity to signals of betrayal, produces partners who conceal their
defections and would-be poachers who conceal their interest in your mate. A
classic case of misdirection occurred in Vladimir Nabokov’s novel
Laughter
in the Dark
. The central character is a wealthy, respectable businessman
named Albinus, who pursues art and cinema as hobbies. After a long period of
fantasizing about it, Albinus leaves his wife and starts to live with his young
mistress, named Margo Peters. Unbeknownst to Albinus, Margo begins to scheme to
fleece him of his money. In time, Albinus hires an artist named Axel Rex to
indulge his fantasy for producing a new kind of movie. Albinus remains in the
dark about the fact that Rex and Margo had previously been lovers. Before long,
Margo and Rex resume their torrid affair. Axel Rex delights in carrying out the
deception right under Albinus’s nose. When Albinus begins to grow suspicious,
Rex uses an interesting ruse—he pretends to be gay. Margo joins Rex in the
deception, declaring her contempt for Rex’s feminine mannerisms. With these
deceptions in place, Margo and Rex succeed in allaying Albinus’s suspicions,
and Rex is allowed to become a common presence in their household while
cuckolding Albinus at every opportunity.

Co-evolution continues. Concealment, which evolved as a response
to a partner’s jealousy, now produces an increased sensitivity to subtle signs
of treachery. Jealousy becomes more easily activated. In
Laughter in the
Dark,
a car accident renders Albinus literally blind, a metaphor for his
psychological blindness. His inability to “see” Margo and Rex’s deception led
to his inability to see at all. He moves uneasily with a cane, bumping into
objects as he stumbles through the darkness. But over time, his physical
blindness improves his psychological sensitivity. He begins to hear the
laughter in the dark. And for the first time, psychologically, he begins to
“see.” Over evolutionary time, those who got duped failed to reproduce as
successfully as those with psychological antennae attuned to deception. So
humans have become incredibly skillful detectors of deception, just as we are
adept at carrying out deception.

The spiral continues unabated, as long as the conflicts of
interest between men and women continue. In some cases, the good sleuth wins,
the deception is successfully detected, and the threat to the relationship is
skillfully vanquished. In other cases, the betrayer wins. And in some cases,
there is no clear winner. When Albinus finally hears the laughter in his
darkness, Axel Rex and Margo are forced to flee. Although they manage to cheat
Albinus sexually and monetarily, his emerging psychological sensitivity to
betrayal helps him to staunch the losses. He returns to his wife and seeks
revenge on his betrayers. At this moment in the evolution of our species, we
are all end products of the co-evolutionary process that has produced an
exquisite capacity for romantic deception as well as a great capacity for
detecting it.

Now consider another co-evolutionary spiral involving jealousy.
Although it is primarily a defense against a partner’s defection, the intensity
of jealousy also reveals to the partner information about the strength of
commitment. People correctly interpret the total absence of jealousy as failure
to be sufficiently committed to the relationship. Imagine that you started
passionately kissing someone else at a party while your partner looked on, all
the while displaying not the slightest sign of being upset. You would almost
certainly wonder whether your partner really cared about you, or even had a
pulse. Absence of jealousy signals lack of love.

People interpret moderate jealousy, in contrast, as a sign that
their partner feels committed to them, but excessive jealousy signals danger.
Men and women interpret excessive jealousy as a sign of anxiety about the
relationship. They sense correctly that the partner feels perpetually
threatened by real or imagined rivals.

How do these signals enter into the co-evolutionary arms race of
jealousy? Women have developed a strategy of
intentionally evoking
jealousy by strategically flirting with other men in their partner’s presence.
Why trip an emotional switch and risk jealous violence? First, by evoking
jealousy, women increase the man’s perception of their desirability. A man who
takes his girlfriend for granted, for example, might come to believe (or be
reminded) that she is a real “babe” after rivals start sniffing around. Second,
evoking jealousy provides a litmus test for the woman. By gauging the partner’s
response, she can evaluate the strength of his commitment. If he is indifferent
to her flirtations with other men, it signals the lack of commitment; if he
gets jealous, it signals the depth of his emotional involvement. Third, evoking
jealousy increases a man’s commitment. By convincing the partner that he is
surrounded by rivals, the man comes to believe that he is extraordinarily lucky
to be with his partner, and thus strengthens his commitment to her.

In principle, this should set the stage for yet another spiral
in the co-evolutionary process. Men are not merely passive puppets at the hands
of women, having their jealousy strings tightened and slackened at women’s
whim—at least not all the time. They learn to distinguish real threats from
false alarms, to separate a mate’s casual flirtation from real sexual interest
in a rival. But we live in a social world filled with uncertainty. A person’s
smile may be the most ambiguous signal in the mating universe, so it’s often
hard to know if it signifies casual flirting, real sexual interest, or merely
friendliness.

These examples give some flavor of the co-evolutionary spirals
that have evolved over time in the intricate dance of men and women in romantic
relationships. The next chapter explores how women and men do this dance
differently.

Jealousy on Mars and Venus

The female of the species is more deadly than the male.

—Rudyard Kipling

C
OUPLE THERAPIST AND AUTHOR
John Gray argues that, when it comes
to relationships, men seem like they are from Mars, women from Venus. Are men
more jealous than women? Or are women more jealous than men? Literature, drama,
and movies often depict men as the jealous sex. Shakespeare’s Othello was
consumed with jealousy, for example, and it is hard to find comparable dramatic
cases portraying women. Common lore, on the other hand, notes that “hell hath
no fury like a woman scorned,” suggesting that women might react more intensely
to a betrayal or defection. What do the scientific studies show about which sex
is most jealous?