Identical twins may demonstrate remarkable similarities in traits, influenced by their common genetic structure. On the other hand, as 48 Hours Correspondent Erin Moriarty finds out, genes don't account for all behavior.
Debbie Melhman and Sharon Poset eat alike - they both enjoy their cereal doused with half-and-half. They talk alike and have almost equivalent IQs. Not surprisingly, they are identical twins. What is surprising, however, is that these two have only known each other - and been aware of each other's existence - for a year and a half.
Separated at birth, Debbie and Sharon were adopted by different families. Debbie didn't even know she'd been adopted until age 45. She also learned then she had a twin.
At that point, Debbie, who was living in Connecticut, hired a private detective. Within 24 hours, he found Sharon in Kentucky. Sharon had known she was adopted, but had been unaware of her twin. At first, she was reluctant to return Debbie's call.
But as soon as they met, they discovered similarities. Says Sharon: "I look at her and go, 'In high school did you have one eyebrow?' And I look at her and die laughing."
They have an astounding number of shared traits. Both are chronically late, cross their eyes when excited and sported identical hairstyles at almost every age.
How do they explain it? Debbie believes it's all in their genes.
Stories like this can be a little disconcerting, especially for parents trying to rear well-behaved kids. If twins like Debbie and Sharon - raised in different homes - turn out so alike, maybe environment doesn't matter as much as we think. Maybe a big piece of who we are, and who we become, is programmed into our genes.
Psychologist and twin researcher Nancy Segal, author of Entwined Lives, says that genes influence almost every facet of our lives. Genes affect choice of careers and hobbies, political beliefs, taste in clothing and food, as well as tendencies towards hyperactivity, anorexia, bulimia and seizures.
Segal discovered all this by studying dozens of twins separated at birth, she says.
One pair, Jerry and Mark Levey, were adopted as babies by different families. They finally met at age 31 when a friend of Mark's noticed a startling resemblance and arranged for a get-together. They quickly realized remarkable affinities.
Both Leveys are volunteer firefighters. They both drink Budweiser beer, holding the can the same way (with a pinky under the bottom). Their back hair even curls the same way. They had weighed the same until a year before they met, when Jerry went on a diet. Mark now weighs almost 100 pounds more than his brother.
This difference in pounds is important since it demonstrates the limits of our genes and the power of free will, says Segal. "Remember: Genes don't tell us what to do. Genes just predispose us to certain events or opportunities and we decide how to act," she says.
Identicl twins such as the McKinneys illustrate yet another point. The same parents raised Conrad and Perry McKinney - together in the same house. They attended the same schools. They even went into business together.
Conrad is a martial arts expert, a health nut and a private detective. This profession comes in handy for someone who wants to, say, find out what's happening to his brother. Because these days, catching up with Perry isn't so easy. He is a homeless alcoholic.
No one really knows why these two went in such different directions. Perry claims it was just a choice. But it may also have been the different experiences each twin had as an adult. Whatever the reason, the lives of these identical twins - maybe of most identical twins - underscore a point: Your genes may count for a lot, but they don't count for everything.
Says Perry: "We have our own identities. He is he. I am me. Period. The way it should be."
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