As of 2009, 33.3 births out of 1,000 are of twins in the US. A few of these twin pairs end up becoming separated for various reasons, especially during adoptions. For researchers in the fields of genetics and psychology, separated twins, especially identical twins, offer a unique insight into the long-running debate of nature versus nurture. While some argue that genetics play an important role in creating our personality thus implying that identical twins would have similar personalities no matter what, others believe that the environment they grow up in has a greater influence. In the case of “Jim twins,” however, the debate seems to favor nature, and here’s more about it.

Identical twins, Jim Lewis and Jim Springer, were separated four weeks after their birth and adopted by different families. When they finally met 39 years later in 1979, they were astonished by how surprisingly similar their lives had been. 

Jim Lewis did not know he had a twin brother until he was five years old, though it never occurred to him to look for his twin until he was 38. Jim Springer came to know about his brother when he was eight years old, but both he and his adoptive parents thought Lewis was dead. In 1977, Lewis decided to look for his brother and found the name Springer through a courthouse where he lived. They spoke on the phone and finally met in 1979.

Lewis and Springer lived only 45 miles apart in Ohio. They both married twice to women with the same names, named both their dogs “Toy,” and even gave their sons the same name. 

Apart from having the same first name, both the twins have unbelievable similarities in their lives. They were six feet tall and weighed exactly 180 pounds. They both had a light blue Chevrolet which they drove to Pas Grille Beach in Florida for a family vacation. They held a part-time sheriff post, were habitual fingernail biters, smoked Salem cigarettes, and had migraines. Both their first wives were named “Linda” and their second wives “Betty.” They also enjoyed leaving notes throughout the house for their wives. One of them named his son “James Allan” and the other named his son “James Alan.”

According to the Minnesota Study of Twins Reared Apart, there were also several differences. While one wore his hair combed straight, hanging down over his forehead like the Beatles, the other swept it back and had sideburns. One expressed himself much better through speech while the other found it easier to do in writing. Though both of them married twice, one of them married a third time to a woman named Sandy.

In 1979, researchers at University of Minnesota conducted a study of 137 pairs of twins over a period of 20 years and found that genetics contributes more significantly to a person’s personality than previously thought. 

The “Jim twins” were one of the pairs that were studied by the researchers. Of the 137 pairs, 81 were identical twins, that is they were born from a single, fertilized egg that split into two, and 56 were fraternal twins, twins born from two different eggs fertilized by two different sperms. The findings of the Minnesota study also launched a debate on effects of nature versus nurture on a child. Another study by Science journal found that about 70% of IQ variation among twins is genetic while only 30% was environmental. Identical twins raised apart were also found more likely to be either religious or not religious.

Recently scientists have identified a third factor, epigenetics, while studying identical twins with different medical histories. Understanding this, they believe, will help cure genetically inherited disorders such as autism in the future. 

Epigenetics is the study of changes in gene function that are inheritable but which do not involve changes in the DNA sequence. Scientists found that identical twins are epigenetically indistinguishable during the early years of their life, but there are remarkable differences in the older twins. Twins who spent less time together and/or had different medical histories showed greater differences.

Andrew Feinberg, director of the Center for Epigenetics at Johns Hopkins School of Medicine, studied a pair of twins, Sam and John, who were diagnosed with autism spectrum. John was born with a congenital heart defect for which he underwent surgery at three and a half months of age. Though Sam has challenges too, especially with social skills, John’s symptoms are far severe. According to Feinberg, though the research is still in its early stages, understanding how epigenetics influence disorders such as autism could help correct them since, unlike our DNA sequences, epigenetic processes can be altered.

[sources: LiveScience, NationalGeographic]