Attracted to That Healthy Glow? : Science: You think you’re a sucker for a pretty face, but evolutionary biologist Randy Thornhill thinks what you’re really going ga-ga over is a potent immune system.
Prof. Randy Thornhill is studying the languorous, lingerie-clad form of Stephanie Seymour in a Victoria’s Secret catalogue with clinical detachment.
The model’s pouty lips and prominent cheekbones signal that she has high levels of estrogen, he observes. Ditto for the small lower jaw and overall flatness of her face.
Leafing through the rest of the catalogue, Thornhill finds confirmation of his theories of human beauty on every page.
“The models are just exaggerated forms of attractiveness that is on a continuum,” he says. “They really all look alike when you account for hair color and eye color and that kind of stuff.”
Thornhill, an evolutionary biologist at the University of New Mexico, thinks he knows why we see some women as beautiful and some men as handsome: They display traits--in some cases, influenced by hormones such as estrogen--that we are genetically predisposed to read as signs of a strong immune system. That, in turn, makes them more desirable as potential mates in the age-old battle to see whose genes survive.
It’s a theory sure to make feminists and humanists grit their teeth.
Thornhill rejects the widespread view that influences such as TV commercials and Vogue fashion layouts have conditioned us to see certain people as attractive. Our notions of beauty, he believes, are largely innate.
“We know that people’s judgments of faces are highly correlated,” he says. “You can take pictures from people in one culture and show them to people in another culture and they will rank them the same way.
“There’s clearly something going on with human nature with regard to attractiveness. We think we’re getting it.”
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Thornhill, who at 49 looks a lot like Dick Clark, works out of a small office and lab in the UNM biology department. His desk is littered with papers, a plastic surgery text and the tools of his trade: calipers and a tape measure he uses on volunteer subjects.
A bumper sticker on a file cabinet reads, “Honk if you love Darwin.”
His style is informal, and when he leans back in his chair to chat, his gently elongated vowels betray his Alabama roots. He’s trying to quit smoking, and every so often he tucks a small pouch of smokeless tobacco in his cheek.
Thornhill belongs to a group of scientists who over the last 25 years have applied Charles Darwin’s theory of evolution by selection to people and their behavior.
Modern Darwinists maintain that our primary purpose in life, whether we are aware of it or not, is to transmit our genes to our offspring. It’s an imperative arising from millions of years of evolution.
Modern Darwinism is controversial because its emphasis on the role of genes in behavior seems to endorse stereotypical sex roles while implying that our actions are “programmed.” (Men, according to Modern Darwinists, seek women who can bear many children, and may want to mate with as many women as possible to improve their reproductive odds. Women, on the other hand, are more apt to prefer men who will invest time and resources in helping to raise their young.)
But Thornhill says such objections are ill-founded.
“There’s a lot of misunderstanding about the phenomenon of development,” Thornhill says. “For any trait of the individual, both genes and environment are necessary to get the trait.”
But why would we have evolved a preference for beautiful people in the first place?
In a word, parasites.
Some biologists think our evolution has been driven by competition with viruses, bacteria and other microorganisms that can produce millions of generations in the course of a human lifetime; each generation has a chance to evolve a new adaptation, posing a constant challenge to our immune systems.
People with greater diversity in their genes stand a better chance of evolving new ways to outmaneuver parasites. A key finding is that more genetically diverse individuals tend to have more symmetrical facial and body traits--such features as eyes, hands and feet.
During gestation, and throughout life, the development of these features can be disrupted by infections, toxins, malnutrition and other stresses. The more symmetrical these features are, Thornhill argues, the more they advertise a person’s ability to resist diseases.
Thornhill and a colleague, evolutionary psychologist Steve Gangestad, noted in a 1993 paper (see story, E5) that qualities of averageness and symmetricalness were closely linked with attractiveness, especially in women. But there is another component to attractiveness: Decidedly non-average features, such as a large jaw and prominent cheekbones in men, are rated more attractive by study subjects.
Thornhill suspects this is because such exaggerated features develop during puberty under the influence of testosterone, which is known to suppress immune function. Thornhill reasons that a handsome man is advertising that his immune system is strong if it can withstand the effects of that extra testosterone.
This relentless probing into why some people are considered beautiful might encounter obstacles on many fronts, Thornhill acknowledges.
“My colleagues say some of the things we do here would not be politically correct elsewhere,” he says dryly. “Darwin is the one who did it--he got it all started. He really understood life deeply because he applied an evolutionary perspective.”
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Researchers in other fields are far from convinced that our evolutionary history determines our perception of beauty. They question the methods and underlying assumptions of the new research.
Sarah Nelson, an archeologist and chairman of the University of Denver’s anthropology department, wonders about researchers’ use of questionnaires to elicit people’s attitudes about attractiveness.
“You can structure the answers by the way you ask the question,” she says. And while cross-cultural surveys might seem like a good way to see if there are universal traits of attractiveness, getting unbiased data is difficult.
“The whole world is now contaminated with American movies,” Nelson says, and there is evidence our society’s beauty ideals have been widely assimilated abroad.
“People who go out and do amateur anthropology are missing a lot of the sophistication that goes into anthropological fieldwork,” Nelson says.
More fundamentally, she says, Modern Darwinists are trying to divine the origins of human sexuality using contemporary models of male-female relations.
“This is really reading from our society into the past,” she says. “They have no methodology for considering the past without reference to the present.”
Lois Banner, a historian and chairman of the gender studies program at USC, sees in the new Darwinism the latest in a long line of scientific theories purporting to demonstrate that inequalities between people are “natural.”
In the 19th Century, she notes, scientists used measurements of cranial capacity as “evidence” that men were smarter than women and whites smarter than blacks--all decided on the basis of who had the largest brains. But even after a theory like that becomes discredited, she says, a new one springs up to take its place.
At DePaul University, social psychologist Midge Wilson has studied “lookism”--discrimination on the basis of physical attractiveness. She’s familiar with the notion of biological underpinnings to our perceptions of human beauty, but she doesn’t give the theory much weight.
Given that a biological basis for attraction might exist, she says, “it accounts for such a small part of the picture of what keeps people together and what they might consider attractive.”
Wilson also thinks that changing roles for women, particularly in the workplace, have diminished the importance of their appearance. In this new climate, “Their reproductive fitness is not the only index of their desirability,” she says.
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Thornhill is familiar with such objections. While defending his research methods, he contends most criticism comes from humanities and social sciences scholars whose “egalitarian” ideology doesn’t allow for scientific facts.
“These kinds of criticisms are bothersome because they discredit the scientific knowledge we have of people’s place in nature,” he says. “To argue that some scientific theories have been wrong and that modern evolutionary theory is therefore wrong is typical humanist rhetoric.”
Thornhill realizes that accepting an evolutionary basis for gender differences is tough for many people because it might be used to justify discrimination and other injustices.
Such fears arise from the “naturalist fallacy,” which assumes that because things are by nature a certain way, that is how they ought to be, Thornhill says.
“To say something is evolved is not to say it’s right,” he says. “ ‘Should’ is coming from an entirely different domain than what is or is not.”
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Thornhill doesn’t recall a particular point when he decided to become a biologist, but he remembers a childhood spent collecting insects and snakes and bird-watching.
“Even as a kid I really tuned in to human behavior and psychology,” he says. “It’s been an obsession ever since I can remember.”
When he was in graduate school at the University of Michigan in the early 1970s, Modern Darwinism was the new wave, promising to provide a simple, coherent explanation for the mysteries of human nature.
He knows the idea of genetically encoded impulses and preferences seems to challenge the very notion of free will. It’s an issue he constantly addresses in his undergraduate classes.
Many also wonder whether we are doomed to be blindly driven by primal evolutionary mandates, or whether we can transcend these biological imperatives. Thornhill is optimistic.
“I believe you can, at some level,” he says. “I think self-knowledge gives you more freedom.”
