This is one party where virtually no one shows up alone. Two thousand sets of twins packed into the small city of Twinsburg, Ohio earlier this month to celebrate their twin-ness at a three-day festival called Twins Days. Throughout the weekend, twins marched in the “Double Take” parade, competed in look-alike contests, and snapped photos with one another at a welcome wiener roast on Friday night. Though the festival is meant for twins, there is another group that is just as eager to attend this annual celebration of shared genetics—scientists.
Researchers savor the opportunity of so many twins together at once. By studying, and especially by comparing, data derived from twin sets, researchers working within the hubbub of Twins Days have unlocked valuable secrets for plastic surgeons, psychologists, dentists, dermatologists, criminal investigators, corporate marketers, geneticists, gynecologists, and immunologists over the festival’s 39-year history.
Twins Days hosted its first researcher in 1978—a doctor from Tulane University who traveled from New Orleans to collect hand and footprints, according to an account of the festival’s history written by a former chairman. Since then, dozens of studies have originated in Twinsburg, named for a set of twins—the Wilcox brothers—who lived there shortly after its founding in the 1800s.
This year’s festival theme was “Twinstock—Groovy in Twinsburg!” No matter their age, almost all the twins in attendance dressed alike. Two sets of twins carried matching signs in mock protest of the Vietnam War. A pair of women dressed in pink genie-garb inspired by the popular '70s TV series I Dream of Jeannie.
Though the pairs come for the party, the majority take time during the weekend to file into research tents, two by two, for the sake of science, says Sandy Miller, a member of the organizing committee who has staffed the festival’s headquarters for decades.
“They're very aware that what they are is genetically interesting and the fact that people want to study that is something that resonates with them,” says Dr. Paul Breslin, who has studied twins at the festival as a researcher with the Rutgers University Department of Nutritional Sciences and the Monell Chemical Senses Center, a nonprofit institute in Philadelphia that researches taste and smell. “What makes [Twins Days] a fantastic opportunity is that you can get effectively a year’s worth of data in three days if you really work hard.”
This year, one researcher handed out nose clips and cups of popcorn to twins in a pop-up tent. Dr. Danielle Reed, a geneticist at Monell, had sprinkled the popcorn with a flavor compound called MP-300, which was created in 2004 by Kyowa Hakko Kirin, a Japanese company that manufactures drugs and food additives. The company claims the compound produces a taste sensation known as kokumi—a concept that is popular in Korea but virtually unknown to Americans.
“Americans don't really have a word for it—some people think it means mouthfeel, or when you have a broth, it's that feeling that it's really sustaining and yummy,” Reed says. “There's a sense that kokumi makes food taste much better.” She has tried the additive herself. Her personal review? “Mmm.”
Reed and her team wondered if a person’s ability to taste kokumi, or their preference for it, might have a genetic link. Breslin has shown that the ability to taste umami, a similar savory concept first identified in Japan that is now considered to be one of the five basic tastes, is at least partly dependent on one’s genes.
Not all tastes can be traced to genetics, though—a study by Breslin based on data gathered at Twins Days showed a person’s sensitivity to the sourness of citric acid was highly genetic, while their detection of saltiness in sodium chloride had little to do with their genes.
In her experiment, Reed asked 400 twins to rate the taste of the popcorn for qualities like sweetness, saltiness, and bitterness before jotting down their overall impressions. Back at Monell, Reed will compare the survey results of each twin. If the identical twins she surveyed both gave similar ratings to the taste of the popcorn but fraternal twins rated it differently from one another, then the shared ratings of the identical twins are likely rooted in their shared genetics. If fraternal twins agree on the taste roughly as often as identical twins, or if everyone’s ratings differ dramatically, then the kokumi sensation must be largely a learned phenomenon.
As twin studies have helped to show in the past, rarely is a trait purely genetic or only a product of a person’s environment—more often, it’s a blend. A person’s genes can shape their environment in meaningful ways, and vice versa. This interplay further blurs the lines of how we inherit or acquire traits. Epigenetics obscures that line even further in that specific genes can be turned “on” or “off” and cause variation in traits even among identical twins.
Nevertheless, Reed hopes to trace twin-to-twin variation in the kokumi study back to a particular gene or receptor by mapping the pairs’ preferences for the kokumi-seasoned popcorn onto their genomes. “We look to see where the differences in the DNA might map onto extremeness of kokumi perception,” Reed says. “So for instance, of the people who can really taste it—are they more likely to have a particular genotype and a particular gene?”
Most traits are multigenic and rely on several genes, rather than just one or two. But thanks to surveys from Twins Days, Reed and her colleagues have honed in on a few genes that contribute to specific tastes. The bitterness of brussels sprouts, for example, has been linked to a receptor called TAS2R38, and Reed followed the bitterness of basil back to a receptor called TAS2R60.
“Twins are useful for just getting an idea of, is this a heritable genetic trait and is it worth pursuing in a more in-depth and detailed way?” Breslin says. “It's a very useful first step.”
Geneticists aren’t the only researchers who find a bounty at Twins Days. In a tent near Reed’s, a team from West Virginia University snapped photographs of 360 twins through conventional, infrared, and 3-D cameras. The data will be used by developers to tweak facial recognition software.
“If we can make facial recognition that works well for twins, it should work well for the general population,” says Jeremy Dawson, the team leader and a biometric researcher at West Virginia University. He says current software used in security systems or smartphones still has a hard time distinguishing between mothers and daughters, let alone identical twins.
Meanwhile, Shannon Weitz, a scientist from Proctor & Gamble, ushered 140 sets of identical twins into a trailer for research that will help develop her company’s line of Olay Professional skin care products. She took photos of the twins and recorded their facial measurements. Then, each twin completed a survey on routine habits like sun exposure and hydration. Weitz will pick the twin that looks youngest in the photos and use their survey results to identify which habits may have helped them stave off signs of skin aging.
It’s tough work, mining for all this information at a bustling festival in the heat of summer. The teams frenetically process twins and data to the point of exhaustion, scarcely stopping to eat or drink during 15-hour shifts. “It's about as intense a thing as I've ever done,” Breslin says. The weather, too, can be a problem—in the past, Reed tried to include herbs in her taste trials, but has since abandoned that idea because “Twinsburg is just too hot to try to keep everything fresh.”
And of course the twins are there, first and foremost, to enjoy themselves. “People show up to test with you on taste, after having just had a hot dog that has mustard and relish and ketchup and onions on it and it just makes things difficult,” Breslin says. “Some people might be a little tipsy."
Breslin says it’s all worth it in the end. “We generate incredible volumes of data and we always party when it's over,” he says. “We're so happy to have the data, and we're so happy to be done with it.”
Given the disparate discoveries that can be made by studying twins, the demand for research booths at Twins Days—which the festival caps at 16 per year—isn’t likely to subside for 2015’s 40th annual celebration. "We could probably fill up the whole place with research if we wanted to," says Miller, the festival’s organizer. “But that’s not what Twins Days is about.”
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