The Study of Twins

Twins, especially identical twins, have fascinated humankind for thousands of years. Scientists have been equally enamored with twins because of their usefulness in research. Charles Darwin’s cousin, Francis Galton, was one of the first to suggest in 1875 that studying twins could offer valuable insights into the study of nature versus nurture. Are we more influenced by genes or the environment? Identical, or monozygotic, twins share 100 percent of their DNA. Thus, when scientists compare a particular trait between sets of identical twins and sets of fraternal twins (who are no more alike than any other siblings), they can determine that any additional likenesses between the identical twins are most likely a factor of their genes, rather than the environment. But the research isn’t always fool-proof. For the most part, scientists have found that intelligence is a heritable trait. However, when identical twins were raised in vastly different socioeconomic backgrounds, the twin placed with the poorer family had a lower IQ. So, environment may have an impact on the expression of particular genes.

Although twin studies are being conducted in laboratories and research centers all over the world, they are not without controversy. Josef Mengele, medical director of the Auschwitz-Birkenau concentration camp of World War II, did experiments on 3,000 twins, mostly children, in his effort to create an Aryan race. Only 157 children survived his deadly tests. Fortunately, today’s twin studies are much more reputable and respected. They have provided valuable information on human behavior and health-related issues. One such study showed that autism is largely inherited, a comfort to parents who were told in the past that it was caused by “aloof parenting.”

In addition to established research centers, such as the Twin Studies Center at the California State University Fullerton and the Minnesota Twin Family Study, researchers travel to the annual Twins Days Festival in Twinsburg, Ohio, to sign up identical twins for research studies. Scientists swab saliva, take fingerprints, and fill out questionnaires in an attempt to gather valuable data from twin subjects. Twinsburg attendees have been involved in studies of hearing, fingerprint differences, hair loss, skin diseases, and much more. With DNA testing, twins are also able to confirm whether they are identical or fraternal.

Although some twins may not enjoy being the subject of scientific studies, experts say that most twins feel it’s a privilege to be able to help scientists better understand diseases that affect the human species. Indeed, twins are not only a blessing to their families, but also to medical science and humankind as a whole.

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About Susan Heim

Susan M. Heim is an author and editor, specializing in multiples, parenting, women’s and Christian issues. Her books include "Boosting Your Baby's Brain Power"; "Chicken Soup for the Soul: Twins and More"; "It’s Twins! Parent-to-Parent Advice from Infancy Through Adolescence"; "Twice the Love: Stories of Inspiration for Families with Twins, Multiples and Singletons"; and, "Oh, Baby! 7 Ways a Baby Will Change Your Life the First Year." Upcoming books include "Chicken Soup for the Soul: All in the Family," "Chicken Soup for the Soul: Devotional Stories for Women," and "Moms of Multiples' Devotions to Go." Susan's articles and essays have appeared in many books, magazines and Web sites. She is a member of the National Association of Women Writers and the Southeastern Writers Association, and has a degree in Business Administration from Michigan State University. Susan lives with her husband and four sons (two teenagers and twin grade-schoolers) in Florida.

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