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Understanding Twins

Twin Connections

The study of twins and siblings, and how environment and genes influence us.

Stories about twins and siblings and lookalikes are always riveting. There are the twins reared apart, both of whom edited high school newspapers, studied film, and became writers. Then there are the twins, also reared apart, who both married twice—their first wives were named Linda, their second wives were named Betty—both had sons they named John Allen, and both had dogs named Toy. And of course there's the twin who felt a sharp debilitating pain in her right leg at the very moment her twin sister was in a car accident that... injured her right leg.

Check out these identical twins who, without consulting each other, came up with identical costumes this past Halloween. It’s more than eerie.

Courtesy E. Maran/C Maran
Source: Courtesy E. Maran/C Maran

Such research is important as it explores how environment and genes influence us. This key tool for behavioral geneticists has opened the door onto intelligence, disease, personality, among many areas of inquiry. Certainly, we’d like to blame our genes for all sorts of digressions. Eat too much? Point the finger at your genes. Procrastinate without fail? Again, that blasted DNA.

But environment and genetic makeup actually conspire together to shape us, as pointed out by Nancy Segal, professor of psychology at California State University Fullerton and the director and founder of the Twin Studies Center. She has looked at all manner of data when it comes to twins and siblings. Her investigations, along with that of other researchers, can also tell us a lot about our behaviors, normal or abnormal.

Click here to read about her journey to Bogota, Colombia, where she met two pairs of twins mixed at birth. And for her most recent deep dive, see A Tale of Two Sisters, which chronicles siblings reared apart, both of whom became gymnasts—one a gold-medalist and the other a power tumbler born without legs.


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