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By
Arthur Allen
The Washington Post
Sunday, Jan. 11, 1998

WHY

GENES

AREN'T

EVERYTHING



Nature &
Nurture
When It Comes to Twins,
Sometimes It's Hard
To Tell the Two Apart

Sherry and Sharon Clark
Twins Sherry and Sharon Clark.
(David Barry/The Post)
There is a mystery
in jazz and a mystery in genes and they are both in the air one night at a D.C. club called Twins Lounge. The owners, identical twins from Ethiopia named Kelly and Maze Tesfaye, are an indistinguishable service dynamo shuttling out of the kitchen with plates of fiery lentil stew and foamy sop-bread. The woman onstage leading a quartet through a medley of jazz standards -- Miss Sharon Clark, by name -- is also an identical twin. She's a bounteous woman in a red sequined dress draped with the long coils of her crimped hair. The band is tight. Sharon's rich, sensuous voice coquets above the piano, the drums, the bass. The sounds merge in harmony and scatter in crazy syncopation, like raindrops becoming rainbows becoming raindrops again.

Between "I Only Have Eyes for You" and "Girl Talk," Sharon trundles over to fix the sound levels and chats up the audience, the way a hard-working entertainer will do. "How's everybody tonight?" she asks abstractedly. Cough, cough. Tap, tap on the microphone. A buzz of feedback. "Now I want to encourage you all to pick up a copy of my new CD," she says. "Sherry's got 'em in the back."

In the back, more or less hidden in shadow, Sharon's identical twin, Sherry, sits with her hands twisted around a big snifter of brandy. Sherry and Sharon are 36 and have always been together. Since childhood they have shared a special language, and they have sung together, and they have counseled each other and argued with each other, and played tricks on their dates and math teachers. But just as no two jazz musicians handle a tune the same way, Sharon and Sherry's riffs on their genetic score have resulted in two distinct ways of life.

On this night, Sherry wears a simple dark dress, and her hair is straightened. Unlike Sharon, who never gets sick, Sherry seems to get whacked by whatever comes down the pike, and at the moment she's recovering from a flare-up of diabetes. She lost 57 pounds on a recent diet and doesn't much look like Sharon these days. And the many ways they are not identical go way below the skin; these twins just move through life differently. Things get to Sherry. "We've always been extremely close and had a very strong bond. But I've always been more cautious, always seeking acceptance," she says, gripping the brandy as she watches Sharon flirt with the piano player. "You know, Sharon never gets nervous at her gigs. But I do."

Identical twins are the clones of nature, each descended from the symmetrical splitting of a single fertilized egg into cells that contain the identical sequence of billions of even tinier DNA molecules. They occur about once every 250 births, which makes them about a third as common in America as fraternal twins, who descend from two separately fertilized eggs and are no more similar genetically than other siblings.

Identical twins are far more familiar than, say, septuplets, but there is still something a little eerie about them, from the double-your-pleasure Doublemint girls to the ghost girls haunting the snowbound lodge in "The Shining." Maybe it's the disorientation induced by a human optical illusion. Maybe it's the fungibility of existence suggested by two lives apparently as interchangeable as bootleg videotapes. If a twin's fate is demonstrably linked to her double's by invisible clumps of nucleic acid, does that mean the rest of us are just as dominated by our DNA? How important are genes, anyway, in determining whether people are beautiful or ugly, stupid or smart, violent or meek, worried or blissful? Are Hell's Angels really born to lose, as it says on their helmets, or were they just brought up wrong?

In the case of the Clark girls, Sharon Inez, 6 pounds 15 ounces, was born at 10:49 a.m. on December 21, 1961, at Fort Belvoir Hospital, where her father, Staff Sgt. Curtis Clark, was a water purification specialist. Seven minutes later Sherry Lynn entered the world, half an inch longer but eight ounces lighter. When the twins were a year old, their mother, Mary, noted in her baby book that Sharon "eats very good except for the usual messiness. Likes all foods except spinach." As for Sherry, she "fusses at all mealtimes, but loves spinach."

Growing up together in a big household in a semirural corner of Alexandria, the twins were a source of family amusement. At age 3, their older sisters, Sylvia, Tina and Rosalind, would plunk them down in little chairs and dress them as royalty. Sharon, in knee socks and a towel turban, would be the king. Sherry was the queen, festooned with costume jewelry. "Sharon would have this exuberant clowning expression all the time, while Sherry was always more serious-looking, even as a baby," says Tina. "That was one of the ways we could tell them apart." Sharon was headstrong and heedless; Sherry was polite and careful. Sherry was sugar, Sharon spice.

At school, the girls excelled in drama and song, learning from their father's jazz collection -- "cocoa music," they called it in their secret language. They were heavy girls and very dark-skinned, and made to feel bad about it, especially when they passed through Soul Corner, the yellow brick corridor at Fort Hunt High School where the tough kids hung out. The daily initiation rite on that patch of turf provided a clue on how the twins would confront life's adversities. Sherry would go out of her way to avoid the taunts of Soul Corner. Sharon plunged right through, elbows at the ready, giving as good as she got. "Sharon," recalls Sherry, "would go to bed with her fists balled up in case anybody messed with her in her dreams." Sherry, on the other hand, was not as resilient. At age 13, she attempted suicide by swallowing pills. And a year later, after their father died suddenly of heart failure, Sharon became Sherry's protector.

If the Clark twins both had exactly the same DNA, how was it that from infancy their personalities were so distinct? Was it a subtle shading of parental affection that accounted for Sharon's brashness and Sherry's anxiety? Or something that happened in the womb? Was it the kind of invisible, indelible influence that behavior geneticists, who try to divide influences on personality into neat categories -- genes or environment -- simply throw up their hands about and call "noise," which is the scientific equivalent of a shrug?

Although the Clarks are one of 15,000 twin pairs in an ongoing study of human behavior at Virginia Commonwealth University, the scientists who mail Sherry and Sharon questionnaires every several years don't presume to know the women's whys and wherefores. The biological history of any individual is a Tower of Babel in which nature and nurture are virtually inseparable. "Science," in the words of the study's co-director, Lindon J. Eaves, "generally does a good job of dealing with the statistical properties of aggregates. It does a lousy job of dealing with the behavior of individual particles."

But individual particles, of course, are what interest most of us in our individualistic culture. And at the level of particles, the nature-nurture debate, a scientific controversy that has been raging for more than a century, is all about our limits -- about whether they come from outside or within. Whether we are what we are because our genes programmed us that way, or because environment -- be it womb, home, neighborhood or nation -- shaped us.

It is a debate that has often been tipped one way or another by shifts in public opinion. There was a time early this century when scientists tried to create a kind of animal husbandry for humans that aimed, in the words of its founder, Sir Francis Galton, to "check the birth rate of the unfit" and "improve the race" by promoting "early marriages of the best stock." The Nazis took Galton's idea, which was called eugenics, to its notorious extreme, and in the horrific failure of their master race rendered the idea of tinkering with the human gene pool unfit for a generation. In the postwar era, bolstered by the ideas of anthropologist Franz Boas and psychologist B.F. Skinner, among others, nurture took over. People weren't intrinsically good or bad stock; it was how mama raised the kids, and the social context she raised them in, that accounted for whether they became bums or angels.

Now the pendulum has swung again. Nurture is out, nature is back. And science is largely the reason why.

Every week, it seems, comes a new revelation about who we are and why we are, all attributable to our genetic code. So amazing are these discoveries that they seem in need of exclamation points and screaming headline type: We've isolated the gene that determines sexual orientation! We've isolated the gene that causes breast cancer! We've isolated the gene that determines whether we will become substance-addicted! It's as if we are on the brink of being able to alter fate through genetic engineering, one person at a time.

In truth, the discoveries have proved to be more complicated than they might appear at first glance, but they portend an ability to unlock in the laboratory some of the mysteries of life. Well before molecular genetics gained center stage, however, scientists had -- and continue to have -- another way of approaching these mysteries, and that's through the mysteries that are twins.

(continued on Page Two)

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