The last time you had sex, there was arguably not a thought in your head.
Okay, if it was very familiar sex with a very familiar partner, the kind
that – truth be told – you probably have most of the time, your mind might
have wandered off to such decidedly nonerotic matters as balancing your
cheque book.
But if it was that kind of sex that is the whole reason why you took up having
sex in the first place – the out-of-breath, out-of-body,
can-you-believe-this-is-actually-happening kind of sex – the rational
version of you had probably taken a powder.
Losing our faculties over a matter like sex ought not to make much sense for a
species like ours that relies on its wits. A savanna full of preda-tors,
after all, was not a place to get distracted. But the lure of losing our
faculties is one of the things that makes sex thrilling – and one of the
things that keeps the species going.
As far as your genes are concerned, your principal job while you’re alive is
to conceive offspring, bring them to adulthood and then obligingly die so
that you don’t consume resources better spent on the young. But mating and
the rituals surrounding it make us come unhinged in other ways, too: ones
that are harder to explain by the mere babymaking imperative.
There is the transcendent sense of tenderness you feel towards a person who
sparks your interest. There is the sublime feeling of relief and reward when
that interest is returned. There are the flowers you buy and the poetry you
write and the impulsive trip you make to the other side of the world just so
you can spend 48 hours in the presence of a lover who is far away. That’s an
awful lot of busy work just to get a sperm to meet an egg – if merely
getting a sperm to meet an egg is really all that it’s about.
What scientists, not to mention the rest of us, want to know is: why? What
makes us go so loony over love? Why would we bother with this elaborate
exercise in fan dances and flirtations, winking and signalling, joy and
sorrow?
“We have only a very limited understanding of what romance is in a scientific
sense,” admits John Ban-croft, emeritus director of the Kinsey Institute.
But that limited understanding is expanding. The more scientists look, the
more they are able to tease romance apart into its individual strands – the
visual, auditory, olfactory, tactile, neurochemical processes that make it
possible. None of those things is necessary for simple procreation, but all
of them appear essential for something larger. What that something is – and
how we achieve it – is only now coming clear.
If human reproductive behaviour is a complicated thing, part of the reason is
that it’s designed to serve two clashing purposes. On the one hand we are
driven to mate a lot. On the other hand we want to mate well so that our
offspring survive. If you’re a female, you get only a few rolls of the
reproductive dice in a lifetime. If you’re a male, your freedom to conceive
is limited only by the availability of willing partners, but the demands of
providing for too big a brood are a powerful incentive to limit your
pairings to the female who will give you just a few strong young. For that
reason, no sooner do we reach sexual maturity than we learn to look for
signals of good genes and reproductive fitness in potential partners and to
display them ourselves.
“Every living human is a descendant of a long line of successful maters,” says
David Buss, an evolutionary psychologist at Texas University. “We’ve adapted
to pick certain types of mates and to fulfil the desires of the opposite
sex.” One of the most primal of those desires is that a possible partner
smells right. Good smells and bad smells are fundamentally no different from
each other; both are merely volatile molecules wafting off an object and
providing some clue as to the thing that emitted them.
Humans, like all animals, quickly learn to assign values to those scents,
recognising that, say, putrefying flesh can carry disease and thus recoiling
from its smell and that warm cookies carry the promise of vanilla, sugar and
butter and thus being drawn to them.
Scent not only tells males which females are primed to conceive, but also lets
both sexes narrow their choices of potential partners. Among the
constellation of genes that control the immune system are those known as the
major histocompatibility complex (MHC), which influence tissue rejection.
Conceive a child with a person whose MHC is too similar to your own and the
risk increases that the womb will expel the foetus. Find a partner with
sufficiently different MHC and you are likelier to carry a baby to term.
Studies show that laboratory mice can smell too-similar MHC in the urine of
other mice and will avoid mating with those individuals. In later work
conducted at Bern University in Switzerland, human females were asked to
smell T-shirts worn by anonymous males and then pick which ones appealed to
them. Time and again they chose the ones worn by men with a safely different
MHC.
If the smell of MHC isn’t a deal-maker or breaker, the taste is. Saliva also
contains the compound, a fact that Martie Haselton, an associate professor
of psychology at the University of California, Los Angeles, believes might
partly explain the custom of kissing, particularly those protracted sessions
that stop short of intercourse. “Kissing,” she says simply, “might be a
taste test.”
Precise as the MHC-detection system is, it can be confounded. One thing that
throws us off the scent is the birth-control pill. Women who are on the pill
– which chemically simulates pregnancy – tend to choose wrong in the T-shirt
test. When they discontinue the daily hormone dose, the protective smell
mechanism kicks back in. “A colleague of mine wonders if the pill may
contribute to divorce,” says Charles Wysocki of the Monell Chemical Senses
Center in Philadelphia. “Women pick a husband when they’re on birth control,
then quit to have a baby and realise they’ve made a mistake.”
Less surprising than the importance of the way a partner smells is the way
that partner looks and sounds. Humans are suckers for an attractive face and
a sexy shape. Men see ample breasts and broad hips as indicators of a
woman’s ability to bear and nurse children – although most don’t think about
such matters so lucidly. Women see a broad chest and shoulders as a sign of
someone who can clobber a steady supply of meat and keep lions away from the
cave. And while a hairy chest and a full beard have fallen out of favour in
the waxed and buffed 21st century, they are historically seen as signs of a
healthy testosterone flow that gives rise to both fertility and strength.
A deep voice, also testosterone-driven, can have similarly seductive power.
The internal chemical tempest that draws us together hits Category 5 when
sex gets involved. If it’s easy for a glance to become a kiss and a kiss to
become much more, that’s because your system is tripwired to make it hard to
turn back once you’re aroused. That the kiss is the first snare is no
accident.
Not only does kissing serve the utilitarian purpose of providing a sample of
MHC, but it also magnifies the other attraction signals – if only as a
result of proximity. Scent is amplified up close, as are sounds and breaths
and other cues. And none of that begins to touch the tactile experience that
was entirely lacking until intimate contact was made. “At the moment of a
kiss, there’s a rich and complicated exchange of postural, physical and
chemical information,” says Gordon Gallup, a psychologist who co-authored a
study at Albany University, New York, about which voices people found
attractive. “There are hardwired mechanisms that process all this.”
What’s more, every kiss may also carry a chemical Mickey, slipped in by the
male. Although testosterone is found in higher concentrations in men than in
women, it is present in both genders and is critical in maintaining arousal
states. Traces of testosterone make it into men’s saliva and it’s possible
that a lot of kissing over a long period might be a way to pass some of that
natural aphrodisiac to the woman.
If we’ve succeeded in becoming such efficient reproductive machines – equipped
with both a generous appetite for mates and a cool ability to screen them
for genetic qualities – why muddy things up with romance? For one thing, we
might not be able to help it. Just being attracted to someone doesn’t mean
that person is attracted back and few things drive us crazier than wanting
something we may not get.
Cultural customs that warn against sex on the first date emerged for such
practical reasons as avoiding pregnancy or sexually transmitted diseases,
but they’re also there for tactical reasons. Males or females who volunteer
their babymaking services too freely might not be offering up very valuable
genes. Those who seem more discerning are likelier to be holding a winning
genetic hand – and are in a better position to demand one in return.
The elaborate ritual of dating is how this screening takes place. It’s when
that process pays off – when you finally feel you’ve found the right person
– that the truelove thrill hits and studies of the brain with functional
magnetic resonance imagers (fMRIs) show why it feels so good.
The earliest fMRIs of brains in love were taken in 2000 and revealed that the
sensation of romance is processed in three areas. The first is the ventral
tegmental which is the body’s central refinery for dopamine. Dopamine
regulates reward. When you win a hand of poker, it’s a dopamine jolt that’s
responsible for the thrill that follows.
Helen Fisher, an anthropologist at Rutgers University, New Jersey, and an
expert on romance research, has conducted recent fMRI scans of people who
are not just in love but newly in love. “This little factory near the base
of the brain is sending dopamine to higher regions,” she says. “It creates
craving, motivation, goal-oriented behaviour – and ecstasy.”
Something has to turn the exhilaration of a new partner into what can approach
an obsession and that something is the brain’s nucleus accum-bens, which
processes thrill signals. The last stop for love signals are the caudate
nuclei. It’s here that patterns and mundane habits, such as knowing how to
type and drive a car, are stored. Motor skills like those can be hard to
lose, thanks to the caudate nuclei’s indelible memory. Apply the same
permanence to love and it’s no wonder that early passion can gel so quickly
into enduring commitment.
The problem with romance is that it doesn’t always deliver the goods. For all
the joy it promises, it can also play us for fools, particularly when it
convinces us that we’ve found the right person, only to upend our
expectations later. Birth-control pills that mask a woman’s ability to
detect her mate’s incompatible MHC are one way that bad love can slip past
our perimeters. Adrenaline is another. Any overwhelming emotional experience
that ratchets up your sensory system can distort your perceptions,
persuading you to take a chance on someone you should avoid.
Arthur Aron, a psychologist at the State University of New York, says people
who meet during a crisis – an emergency landing of an aircraft, say – might
be much more inclined to believe they’ve found the person meant for them.
“It’s not that we fall in love with such people because they’re immensely
attractive,” he says. “It’s that they seem immensely attractive because
we’ve fallen in love with them.”
If that sounds a lot like what happens when people meet and date under the
regular influence of drugs or alcohol, only to sober up later and wonder
what in the world they were thinking, that’s because in both cases powerful
chemistry is running the show. When hormones and natural opioids get
activated, says Jim Pfaus, a psychologist and sex researcher at Concordia
University in Montreal, you start drawing connections to the person who was
present when those good feelings were created. “You think someone made you
feel good,” Pfaus says, “but really it’s your brain that made you feel good.”
Of course, even a love fever that’s healthily shared breaks eventually, if
only because – like any fever – it’s unsustainable over time. Fisher sees
the dangers of this type of love in fMRI studies she is conducting of people
who have been rejected by a lover and can’t shake the pain. In these
subjects, as with all people in love, there is activity in the caudate
nucleus, but it’s specifically in a part that’s next to a brain region
associated with addiction. If the two areas indeed overlap, as Fisher
suspects, that helps to explain why telling a jilted lover it’s time to move
on can be fruitless – as fruitless as admonishing a drunk to put a cork in
the bottle.
Happily, romance needn’t come to ruin. Even irrational animals like ourselves
would have quit trying if the bet didn’t pay off sometimes. The eventual
goal of any couple is to pass beyond serial dating – beyond even the thrill
of early love – and into what’s known as companionate love. That’s the
coffee-and-Sunday-paper phase and the fact is, there’s not a lick of
excitement about it. But that, for better or worse, is adaptive too.
If partners are going to stay together for the years of care that children
require, they need a love that bonds them to each other but without the
passion that would be a distraction. As early humans relied more on their
brainpower to survive – and the dependency period of babies lengthened to
allow for the necessary learning – companionate bonding probably became more
pronounced.
Calling something like love mundane, of course, is true only as far as it
goes. Survival of a species is a ruthless and reductionist matter, but if
staying alive were truly all it was about, might we not have arrived at ways
to do it without joy – as we could have developed language without
literature, rhythm without song, movement without dance?
Romance might be nothing more than reproductive filigree, a bit of decoration
that makes us want to perpetuate the species and ensures that we do it
right. But nothing could convince a person in love that there isn’t
something more at work – and the fact is, none of us would want to be
convinced. That’s a nut that science may never fully crack.
Additional reporting: Eben Harrell, Kristin Kloberd, Kate Stinchfield
This is an edited version of an article that first appeared in Time magazine
How it works
Liking what we hear
Men with deep voices are perceived as having a high testosterone level and in
one study were shown to have more children
The lure of smell
Men and women respond to each other’s MHC – part of the genetic make-up of the
immune system, which helps to determine whether a foetus will be carried to
term
When love dies
Lovers who meet under the influence of alcohol or drugs or during an
adrenaline surge may cool off when their bodies return to normal
Why we do it
Nature doesn’t care if we enjoy falling in love; it wants us to care for our
children. When we find someone to mate with, romance focuses us, and love
bonds us for the child-rearing years and beyond
