Decoding desire The science of sexiness Researchers

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Decoding desire The science of sexiness Researchers Powered By Docstoc

by Anne Machalinski, Aili McConnon and Christie Nicholson

Decoding desire: The science of sexiness
Researchers say attraction is more than meets the eye. A woman’s curves and
a man’s magnetic dance moves signal healthier genes.

Romeo and Juliet. Princess Leia and Han Solo. Brad and Angelina. They all have that electric
sexual connection. From literature to the silver screen to the high school dance floor, attraction,
desire and chemistry are universal. But still for most of us, this intangible vibe remains mystifying.

Start with the fact that we are wired with a drive to pass our genes to future generations. This is,
after all, the root motive for mating. Guided by this motive, scientists are now beginning to reveal the
subtle, yet determined, cues of sexual attraction. Body proportion and the symmetry of facial and
body features serve as visual proxies for good genes and high fertility, the holy grails in the drive to
procreate. Skills on the dance floor, sweaty tee shirts and sultry voices also play curious roles in the
hunt for a mate.

“Mating is so critical to our survival,” said Helen Fisher, an evolutionary anthropologist at Rutgers
University. “We are just hitting the tip of the iceberg of finding these evolutionary cues that steer us,
unconsciously, through this sea of mating to the island of reproduction.”

With that, a new era in reproduction studies has emerged, untangling this complicated question of
chemistry. But the field, so fundamental to human evolution, has been fraught politically.
Evolutionary studies started in the 1930s, said Fisher, but quickly fell out of favor during WWII and
its aftermath, when biological differences were used to buttress anti-Semitism and other forms of

Then in the 1960s, primatologist Jane Goodall studied chimpanzees and realized they appeared
“unnervingly human,” said Fisher.

Chimps, our closest animal relatives, who are completely separate from human culture, also feel
love, anger and desire. This proved something other than social influences molded our behavior.
These emotional traits were genetic, Goodall’s research revealed.

With this discovery, evolutionary theory blossomed. And when studying evolution, reproduction is
the place to start. How we chose our mate determines the route our DNA will take into the next

The start of symmetry studies
The symmetry story begins with the birds and the bees – well, fruit flies. In the 1950s, studies
showed that fruit flies with better immunity were also more symmetrical. To understand symmetry,
imagine an invisible line bisecting an organism’s body. The more one side of the body mirrors the

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other side, the more symmetrical the organism. Later studies of lizards and racehorses revealed
similar health benefits to being symmetrical.

A study with birds showed another surprising correlation: females preferred to mate with symmetrical

Soon after the drive to find connections between human symmetry, health and attraction spurred
research that has been going on for more than 20 years.

Symmetry and dance
Now new research has found that bodily symmetry can also be detected in our twirls and dips on the
dance floor. In December 2005, Robert Trivers, a leading evolutionary biologist, published a paper in
the journal Nature showing that women are wired to notice good dancers. Further, good dancers are
more symmetrical and have better genetic makeup.

Trivers, with scientists from Washington and Rutgers universities, filmed nearly 200 Jamaican teens
dancing. The researchers then asked the teens to rate their peers on a scale of 1 to 10.

“For both sexes, symmetrical individuals were judged to be better dancers,” said Trivers. “We think
symmetry measures developmental stability, the ability of your genes to buffer developmental
stresses.” What they also found was that females were better at detecting symmetry than males

But it turns out women not only see symmetry, they smell it and hear it too.

The smells and sounds of symmetrical people
Randy Thornhill, an evolutionary biologist at the University of New Mexico, gave women the sweaty
tee shirts of men and asked them to pick the ones they liked. Women consistently preferred the
smell of the more symmetrical men. And a fascinating aside: Thornhill also found that symmetrical
men tended to give women more orgasms during intercourse.

Women also prefer the voices of symmetrical men, according to Gordon Gallup, at the University of
Albany. In the days before fire, this may have been the way cave ladies distinguished the hotties in
the dark.

Thornhil’s new studies are revealing that attraction is also related to specific genes. Major histo-
compatibility genes (MHC), for instance, fight parasites and other foreign invaders. People tend to
be attracted to those who have a different MHC from their own for reproductive reasons: children
with a greater variety in MHC are more disease-resistant. Like symmetry, MHC can be detected
through smell, said Thornhill.

Body Mass Index, attraction and health
But other researchers believe that initial attraction isn’t about symmetry at all. Jason Weeden, an
evolutionary psychologist at the University of Pennsylvania, found that men are more attracted to a
specific body-mass index (BMI) and waist-to-hip ratio (WHR), both of which signal fertility.

BMI is calculated by weight in kilograms divided by the square of height in meters.

A healthy BMI is between 20 and 25, said Weeden.

“Women tend to be more attractive around 20…men tend to be more attractive around 25,” he said.

WHR is calculated by measuring waist circumference divided by hip circumference.
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For women, the normal range of WHR is from 0.7 to 0.9, but 0.7 is considered most attractive in
Western women, said Weeden. Both Marilyn Monroe and Kate Moss have a WHR of 0.7, despite
their drastically different sizes. Proportion, apparently, is more critical than BMI in attraction.

While weight and body proportions are not the same thing as symmetry, all three indicate good
physical and reproductive health.

As women fall below the normal BMI range they are considered less attractive and are also in
danger of infertility.

“They lose their reproductive capacity – it’s called amenorrhea,” said Dr. Kerry Page, an assistant
clinical professor in the Department of Medicine at Columbia. “These women stop menstruation, so
they are not fertile.”

Likewise, a BMI above 27 in women can cause serious health problems, such as Type 2 diabetes,
high blood pressure and heart disease.

“There are reproductive consequences of high BMI,” said Page. Obesity can lead to polycystic
ovarian syndrome, when an ovary has multiple cysts, which can result in infertility, she said.

Like BMI, WHR not only determines how attractive a woman is, it also indicates good reproductive

“What a low waist-to-hip ratio tells you is that the woman has a very feminine profile,” said Weeden,
“one that’s conducive to pregnancy.”

The feminine profile is what makes fertile women curvy in the first place. The balance of estrogen in
a woman’s body that causes fat to distribute around the hip and waist in a ratio of 0.7 just so
happens to be the optimal amount of hormone for reproductive success.

These physical cues – symmetry and body shape – are big influences in instant attraction.

“For the short term they [women] go for the kinds of men who will be sexually exciting,” said Trivers.
And the good dancers, being symmetrical, fit that bill.

But for long-term love beware the good dancer, as he may dance off to another opportunity.

Thornhill found that these men are less “lovey dovey” and invest less time in parental care than
asymmetrical men.

“I think the conflict between getting good genes and getting parental investment is a fundamental
one,” said Trivers. On the one hand, good genes can be secured in a one-night stand, but getting a
committed partner is long-term endeavor. And finding this winning combination – good genes and
commitment – in one person can be challenging.

Speed dating
A new study of “speed dating” sheds light on this sharp divide between short-term and long-term

In 2005 Weeden and Robert Kurzban studied more than 10,000 members of HurryDate, a speed
dating company. Dates last for three minutes until a bell alerts people to move on to the next suitor.
Hurry daters meet 25 potential partners in one night.
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This sort of environment offered Weeden and Kurzban a chance to see how people size up mates in
a matter of minutes.

Even though daters, when registering, said they were looking for a long-term partner, their behavior
on these fast dates proved quite the opposite.

Once sitting face-to-face, the daters were attracted not to shared values like education, income or
religion – qualities associated with long-term relationships. Instead women and men both went for
one thing: hot partners.

“It goes from a [long term] set of rules,” says Weeden, “to a set of rules that are about the fun of an
immediate, low-commitment sexual experience.”

Weeden concluded that the essence of the short term/long term distinction is really one of functional
division between mating with a healthy partner and one that will stick around to take care of you and
your children.

As scientists like Trivers, Thornhill and Weeden continue to collect data on the veritable sea of cues
that explain why we are the way we are, many mysteries remain unsolved. For instance, unlike
female BMI, why is the healthiest BMI for men not the most attractive to women?

The future of attraction studies
Advances in brain imaging since the 1990s and the mapping of the human genome in 2000 will
converge with evolutionary work and will mark the next frontier in understanding who we are, said
Fisher. She and her colleagues published a paper in The Journal of Neurophysiology showing that
areas in the brain responsible for passionate desire are the same areas used for hunger and thirst.

Using the recent technology of functional magnetic resonance imaging (fMRI) scientists are able, for
the first time, to essentially map areas of the brain responsible for our thoughts, feelings and
behavior. For instance, they may soon be able to map the causes and control of infatuation, desire
and true love. While they are still far from “mind reading,” they are able to uncover how the brain
controls our behavior in ways they never could before.

Evolutionary research together with this explosion of cutting-edge technology might eventually put
an end to the nature versus nurture debate…and fully explain why we can’t keep our eyes off that
sweaty guy on the dance floor.


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