Twins separated at birth reveal staggering influence of genetics
Twins separated at birth reveal staggering influence of genetic
WASHINGTON Jim Lewis and Jim Springer were identical twins raised apart from the age of 4 weeks. When the twins were finally reunited at the age of 39 in 1979, they discovered they both suffered from tension headaches, were prone to nail biting, smoked Salem cigarettes, drove the same type of car and even vacationed at the same beach in Florida.
The culprit for the odd similarities? Genes.
Genes can help explain why someone is gay or straight, religious or not, brainy or not, and even whether they're likely to develop gum disease, one psychologist explains.
Such broad-ranging genetic effects first came to light in a landmark study Minnesota Twin Family Study conducted from 1979 to 1999, which followed identical and fraternal twins who were separated at an early age. [ Seeing Double: 8 Fascinating Facts About Twins ]
"We were surprised by certain behaviors that showed a genetic influence, such as religiosity [and] social attitudes," said Nancy Segal, an evolutionary psychologist at California State University, Fullerton, who was part of the study for nine years. "Those surprised us, because we thought those certainly must come from the family [environment]," Segal told Live Science. Segal described the groundbreaking research on Aug. 7 here at a meeting of the American Psychological Association.
Born together, raised apart
Researchers at the University of Minnesota, led by Thomas Bouchard, launched the landmark study in 1979. Over the course of 20 years, they studied 137 pairs of twins 81 pairs of identical twins (twins who developed from one egg that split in two), and 56 pairs of fraternal twins (twins who developed from two eggs fertilized by two different sperm).
The Jim twins were probably the most famous set of twins involved in the study, but other pairs were equally fascinating. One pair of female twins in the study were separated from each other at 5 months old, and weren't reunited until age 78, making them the world's longest separated pair in Guinness World Records .
The Minnesota study resulted in more than 170 individual studies focusing on different medical and psychological characteristics.
In one study, the researchers took photographs of the twins, and found that identical twins would stand the same way, while fraternal twins had different postures.
Another study of four pairs of twins found that genetics had a stronger influence on sexual orientation in male twins than in female twins. A recent study in Sweden of 4,000 pairs of twins has replicated these findings, Segal said. [ 5 Myths About Gay People Debunked ]
Nature vs. nurture
A 1986 study that was part of the larger Minnesota study found that genetics plays a larger role on personality than previously thought. Environment affected personality when twins were raised apart, but not when they were raised together, the study suggested.
Reporter Daniel Goleman wrote in The New York Times at the time that genetic makeup was more influential on personality than child rearing a finding he said would launch "fierce debate."
"We never said [family environment] didn't matter," Segal said at the APA meeting. "We just made the point that environment works in ways we hadn't expected."
Another study, commissioned by the editor of the journal Science, looked at genetics and IQ. The Minnesota researchers found that about 70 percent of IQ variation across the twin population was due to genetic differences among people, and 30 percent was due to environmental differences. The finding received both praise and criticism, but an updated study in 2009 containing new sets of twins found a similar correlation between genetics and IQ .
Moreover, a study in 1990 found that genetics account for 50 percent of the religiosity among the population in other words, both identical twins raised apart were more likely to be religious or to be not religious, compared with unrelated individuals.
Other studies found a strong genetic influence on dental or gum health. That research helped to show that gum disease isn't just caused by bacteria, it also has a genetic component, Segal said.
Another study found that happiness and well-being had a 50 percent genetic influence.
In another study, researchers surveyed the separated twins about how close they felt to their newfound sibling. Among identical twins, 80 percent of those surveyed reported feeling closer and more familiar with their twin than they did to their best friends, suggesting a strong genetic component in the bond between identical twins.
The Minnesota study gave scientists a new understanding of the role of genes and environment on human development, Segal said. In the future, twin studies will aim to link specific genes to specific behaviors, as well as investigate epigenetics what turns genes on or off, she said.
Segal, who wrote a book about the study called "Born Together Reared Apart: The Landmark Minnesota Twins Study" (Harvard University Press, 2012), is now doing a prospective study of Chinese twins raised apart, often in different countries, by adoptive families.
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I found this very interesting..
Really interesting article Nona.
I have to agree with Sean on his comment.
Nona,
I have identical twins, and I have read this study. My twins actually are nothing alike, despite the fact that we did everything the same way. It seems that identical twins raised in the same house, will struggle to develop their own identity. There are some things that I can see that nature overrode their desires, like what enjoy doing, but in personality... nothing alike. One is out going, the other is introverted. One is always busy, the other is a procrastinator. One grew her hair long and colored it and the other short. They put their makeup on totally different. I could go on and on, but my point is, I am not really sure if anyone can quantify how much is nature and how much is not only nurture, but also environment.
My girls with a friend.Good point!
Thanks Kav,, so do I..
Oh Perrie, ...they are beautiful! Years ago I had female friends that were identical twins, and hey wee nothing alike in any way ,shape or form. It's very interesting to say the least.
Thanks Nona!
Growing up we had 4 sets of identical twin in my school. All but one set, were totally different. One was totally alike. I have no clue what influences this, only that it's not a cut and dry thing.
Just to be clear, the ''friend'' in the above photo is my identical twin. Yes, it's true, I'm actually that young. I just act older. I have often been told to grow up, but I will continue to act like a child, since I am one.
that it's not a cut and dry thing. It has to be many, many things combined to produce such a unique happening.
Kav...if that's you ...I hope you NEVER grow up
I have younger sisters who are identical twins. They are very dissimilar in attitude, personality, style, interests, hobbies, social circles and just about anything else you can think of.
I think as the younger kids, they got more resources and didn't have to fend for themselves as much as I and my brother did. But they also didnt get the same attention that we got as the first kids. I dont want to say my parents tried harder on me and my brother, but it's kind of the way it is... the first kid is like a precious gem and takes the strictest rules, but by the third and fourth what doesnt kill them right away makes them stronger. They are much younger and are almost a second family for my parents.
I think what came with that was their own internal desire to be different and to be treated differently from each other and from us older siblings. So they developed differently.
I have a set of second cousins who are boys and identical. They are practically the same kid and easy to mix up. They share clothes and friends and hobbies. They are inseparable in a different way. They were the oldest two (with one younger sister) and they always preferred speaking twin talk to each other over interacting with other kids. For them, being the same was a secret club that only they belong to. Their father was non existent and their mother barely acknowledged them. I think their togetherness was their way of having a family.
All in all I think some of the twin'ing behaviors can be influenced by situational settings.
Wow...that's really interesting! Do your twin sisters have special bond with each other? I've heard that wins have a VERY special bond with each other..
I was only home until they were about four because of the age gap. When they were infants, they would only sleep if they were in the same crib. We tried to get them to separate but they would just cry all night. As toddlers they always slept together even though they had separate rooms. They still sleep together as teenagers, but not as often because one of them has a dog that sleeps with her.
They did communicate and still communicate with non verbal cues. I never heard them speak in their own language like my boy second cousins did, but they would often talk to each other in looks and body gestures.
They are much closer to each other than I am with my brother or them.
I find that one of them acts more like my brother and the other acts like me. I get along more with the one that acts like me. I also find it funny that I'm not a huge fan of my sister in law, but the one that acts like my brother really likes her and the one that acts like me doesnt. I think it's a personality difference, but it's really interesting.
I guess that means we're all family
That friend is one lucky dude....