Science

PRIZE SPECIMENS

Fertility drugs have sparked a bumper crop of twins and a field day for geneticists who want to know: do twins hold the key to human nature?

SUE FERGUSON August 30 2004
Science

PRIZE SPECIMENS

Fertility drugs have sparked a bumper crop of twins and a field day for geneticists who want to know: do twins hold the key to human nature?

SUE FERGUSON August 30 2004

PRIZE SPECIMENS

Fertility drugs have sparked a bumper crop of twins and a field day for geneticists who want to know: do twins hold the key to human nature?

Science

SUE FERGUSON

FIFTY-FIVE YEARS AGO, Nancy Grundy and Susan Palanik started life as a single egg. Because that egg likely split sometime between day 1 and 12 after conception, it produced mirror-image identical twins. “If one of us got a tooth on one side,” explains Palanik, “the other would get a tooth on the opposite side.” The same is true for the natural parts in their hair and would be true, they believe, of their handedness had

Palanik not been forced as a child to be like her sister and write with her right hand. Their mirrored symmetry confounded family and friends so much that up into their 30s, says Grundy, their mother would ask them to wear N and S brooches to big family functions.

It also landed their teenage pictures in the Hall of Life display at the Ontario Science Centre in the late 1960s. That wasn’t

the first, or last, time the sisters came under the microscope. They participated in two large tests, the first, a developmental study at age 5, the second, a follow-up developmental and psychological study in their late 20s. Much later, after losing a friend to breast cancer, they were moved to provide mammograms and a health history for a study into the genetic factors influencing breast density. Being poked, prodded or queried, it seems, is part and parcel of living a twin’s life. That’s because their very existence makes them essential to scientists seeking answers to the most fundamental nature/nurture questions in the human experience. Are we born with specific traits or the capacity for certain diseases, or do we merely pick them up along the road of life?

Twins, triplets and other “higher order” multiples have, of course, tweaked the human imagination for centuries: from Greek mythology through Shakespeare to the August issue of Vogue, in which U.S. presidential twins Jenna and Barbara Bush swan about in princess-like gowns. But while our fascination has a long history, today’s multiples face a novel set of circumstances.

Thanks largely to the thousands of infertile couples turning to assisted reproduction technology, which can involve implanting several fertilized eggs in the uterus, twins are in the midst of a population boom. The number of multiple-birth babies in Canada jumped 35 per cent between 1979 and 1999 (while total births fell). One offshoot of this: the Internet is plastered with websites dedicated to twin associations, support groups, family photo albums and diaries crowing over the latest antics of little Ben and Jen. Another development has been the proliferation of twins conferences and festivals, where multiples converge to kibitz and celebrate their unique condition of birth. (Montreal’s Just for Laughs Festival, for example, had a special twins parade this year that drew 2,000 participants.) Meanwhile, all of this is making its way to the lab of human behaviour.

Today’s explosion in the twin population, says Kerry Jang, a University of British Columbia psychologist who heads a 10-year-old investigation into the mental health of500 pairs of adult twins, is “a great thing for science.” Just about anything can—and does—get examined using what’s called the twin method. Seeking genetic clues, researchers have probed

twins for height, weight, heart rate, migraines, depression, social withdrawal, suicidal tendencies, post-traumatic stress disorder, IQ, opposition to authority, poverty, infidelity, empathy, substance abuse, criminality and aggression, to name just some examples. In his 1997 book, How the Mind Works, Canadian-born scientist Steven Pinker, now at Harvard, said the minds of identical twins especially are astonishingly alike, in everything from spelling abilities to hobbies, vices and opinions on such things as the death penalty. “Identical twins separated at birth,” he wrote, “share traits like entering the water backwards and only up to their knees, sitting out elections because they feel insufficiently informed, obsessively counting everything in sight, becoming captain of the volunteer fire department and leaving little love notes around the house for their wives.”

TWINS HOLD THE KEY for scientists deciphering the genetic mysteries of life, explains Daniel Pérusse, a behavioural scientist at the Université de Montréal, because without them geneticists “would be looking for a needle in a haystack.” What’s important is that there are two types of twins, what scientists call a natural experiment: about a third are monozygotic, identical twins who develop when a single fertilized egg splits in two, and thus share the same genes; the rest are dizygotic, fraternal twins who develop when the ovaries release two eggs and, like any siblings, share only 50 per cent of their genes. “If there is a greater resemblance of the trait under study in monozygotic than dizygotic twins,” says Pérusse, then that trait is considered to be influenced more by genetic than environmental factors.

The relationship between personality and finger lengths was the subject of a University of Michigan test that caught Maureen Harper’s eye last winter. After learning about it through a multiples email list she belongs to, the 29-year-old pharmacy technician from Olds, Alta., phoned her fraternal twin sister Corrine Sanderson. “How’d you like to make 50 bucks, U.S.?” she asked. It took more than three hours for each to fill out a questionnaire and photocopy their hands— enough time that Sanderson, who lives in Camrose, Alta., wondered if the money was really worth the effort. Still, she and Harper signed up again this spring for another study on post-traumatic stress disorder, part

of Jang’s UBC investigation. The $25 for another three hours of filling out forms, says Harper, isn’t the point. She’s motivated more by a sense of duty. “We’re never going to learn,” she points out, “if we don’t have guinea pigs.”

So what’s the verdict? Is it nature or nurture that shapes human existence? Well, the answer is still unclear. Since 1979, University of Minnesota researchers have been looking at twins reared in different homes. Their findings suggest there is a strong genetic influence to IQ, for example. But they qualified their conclusions by noting that even twins with separate upbringings shared broadly similar middle class environments. So—the similarities may be as much cultural as genetic. And scientists are really just starting to grapple with the idea that while genes for certain conditions or even personality traits seem to exist, they can lie dormant if nothing in the environment triggers them.

Meanwhile, Pérusse has thrown a wrench into many of the early twin studies by questioning the time-honoured twin method, which allows scientists to compare the two types of twins. Early results from the Quebec Newborn Twin Study, Canada’s first large-scale longitudinal analysis of twins, suggest that because family members tend to treat fraternal twins more as individuals, and identical twins more as a unit, the basis for past comparison could go out the window. Earlier twins studies, Pérusse says, possibly inflated the genetic role.

When you ask twins themselves where they stand on the nature/nurture debate, Grundy and Palanik come down on both sides, with a slight bias towards nature. While their parents treated them as individuals, they’ve nonetheless followed similar paths. With their respective spouses, they’ve been living a few blocks from each other in Pickering, Ont., since their early 20s. The sisters raised their children almost as one big family— Nancy even nursed Susan’s eldest when Susan had difficulties. They’ve spent every birthday together at the family cottage but their 47th, when Grundy was overseas at a Girl Guides’ conference. (Palanik had volunteered with the Boy Scouts.) So, when they both show up somewhere and find themselves in similar outfits—a phenomenon many twins attest to—is that because they’ve shared so many experiences, or because they

share the same genes? “I know we have this connect, but we don’t work hard at improving it,” says Grundy. “People ask, ‘Do you have that mental telepathy thing?’ Well, no. But if we had really worked on it, would we have had it?”

GRUNDY AND PALANIK knew just one other set of twins while growing up. Multiples born after 1978—the year the first testtube baby was born—are likely to encounter far more. When Jennie Maynard takes her five-year-old identical twin sons, Matthew

and Andrew, and 17-month-old son, Charlie, to the park, they can run into as many as seven sets of twins. The Maynards live in Ottawa, Ont., which reputedly has a high multiples population. Studies in Germany, Scotland and Belgium have linked such concentrations to the proximity of certain pollutants, but a high number of couples undergoing fertility treatment could just as easily explain it. Maynard, 35, conceived “her guys,” as she calls them, naturally. But “every time we went out,” she says, “people would ask what fertility doctor we used.” (In fact, fertility drugs, which encourage the

release of multiple eggs, tend to produce fraternal, not identical, twins.)

More recently, however, the curiosity has faded, despite the fact that the boys are, as she calls them, “stereotypical identical twins.” What’s changed? Almost two years ago Andrew started using a wheelchair. Now, she says, “people are more likely to ask, ‘Are they twins?”’ Andrew has cerebral palsy, caused by brain damage in the womb, which affects his major motor skills. It came about because he and Matthew developed twin-totwin transfusion syndrome. The prenatal condition created abnormal blood flow to

the brains of both fetuses, and the lion’s share went to Matthew, who also has CP, but only a mild form.

This is not an isolated situation. “The truth is,” says Dr. Jon Barrett, a specialist in maternal and fetal medicine at Sunnybrook and Women’s College Health Sciences Centre in Toronto, “we’re dealing with a modern epidemic of multiple pregnancies.” And such pregnancies carry many risks. While multiples represent one in 40 births in Canada, they account for one in six preterm births, one in five babies with low birth weight, and one in four babies with very low birth weight (under 3.3 lb.). This puts them, says Donna Launslager, a volunteer with Multiple Births Canada and a Waterloo, Ont., mother of 19-year-old quads, “at a huge risk of dying in the first year.” Many suffer long-term disabilities such as CP, behavioural disorders, or slow language development, the latter because multiples tend to communicate more with each other than their parents.

Even when twins are healthy, Launslager adds, “parents experience overwhelming challenges in caring for, feeding, transporting and paying for them.” When her quads arrived in 1985, she had to quit her job as an insurance underwriter to raise them and their two-year-old brother. In the first year, she and her husband, David, spent $15,000 on diapers, formula, special strollers and the rest. Now, her husband draws a higher salary as a high-school vice-principal, but with five kids in university and college, it’s still a struggle.

Infertility specialists often paper their walls with photos of the twins they’ve delivered, without a single pamphlet on twinto-twin transfusion syndrome or other possible complications in sight, says Launslager, relaying what she’s heard from other multiple birth parents. And, of course, she adds, if you’ve endured years of infertility, “the thought of having two babies sounds like a jackpot.” But she also notes that parents who conceive three or more fetuses are generally encouraged to reduce—that is abortone or two of the eggs. “I just can’t imagine having to face that.”

POPULATION SURGE aside, being a twin is, of course, to be a member of an exclusive club. And this is never more evident than at Twins Days, a two-day festival for multiples billing itself as the largest in the world, now in its 29th year. It’s held the first weekend

in August in—where else?—Twinsburg, Ohio, thus christened in 1823 when Moses and Aaron Wilcox, identical twins who married sisters, had nine children each and later died within hours of each other, settled in this now prosperous community 25 km southeast of Cleveland. Saturday begins with a parade, a veritable exercise in the endless variations of sameness. For more than an hour, twins and triplets—there were no quads or quints this year—snake along the main street, some on floats but most on foot, and many, many, pushing strollers. All shapes, ages and nationalities, they sport togas, swimsuits, army fatigues and T-shirts bearing such slogans as “Womb mates.”

Later, alongside the usual carnival fare of rides and wiener roasts, revellers wander between multiples-specific activities. There are look-alike and—to cover off the relatively small fraternal twin contingent—don’t-lookalike contests. There are also booths pushing “twin Christian cards,” twin scholarships to college, and prenatal health information. In a large research tent, scientists are testing hearing, olfactory systems and skin; or scraping the inside of participants’ cheeks, part of a free DNA test to establish whether they’re identical or fraternal twins for those where appearance doesn’t tell the story. Women make an easy US$10 by filling out a survey on their gynecological history.

That $10 buys lunch for Kathy Bateman and Stefanie Nybom, 32-year-old identical twin sisters celebrating their fourth Twins Days. Kathy, an elementary school teacher from Parham, Ont., and Stefanie, who starts teacher’s college this fall and lives in Ottawa, about 90 km north of Parham, are dressed exactly alike, down to their yellowtinted sunglasses and flowered handbags. When they were growing up, says Stefanie, “everybody wanted us to be different.” They complied, varying their clothes and later their hairstyles, but “deep down,” Kathy confesses, “we always wanted to be alike.”

Sartorial considerations aside, the main reason the two trek to Ohio is for the special camaraderie the festival provides. Today’s twins may well be science’s guinea pigs and society’s good luck or fertility talismans. But in their heart of hearts many appear to belong ultimately only to each other. Hence the appeal of Twinsburg, and sharing time with others like them. “It’s one of the few places.” Stefanie says, “where we’re completely understood.” lui