From Rome’s Romulus and Remus to the movie "The Parent Trap," twins have always fascinated us. But twins may actually prove most valuable in teaching us about how genetics and environment really affect us.

Nancy Segal, a fraternal twin herself who worked on the well-known Minnesota Twin Family Study and authored the book, "Born Together—Reared Apart: The Landmark Minnesota Twin Study,” explains how studying twins has cross-disciplinary impacts, and therefore influences many aspects of our lives.

It’s easy to see the similarities between identical twins, but Segal’s work suggests that we may want to pay more attention to the differences between them. Looking closely at these differences can clue us in on how both nature and nurture shape our character. These differences can also teach us about our health and allow us to come up with better preventative measures and cures for disease.

Segal, who directs the Twin Studies Center at California State University, Fullerton, gives an example of studying twins where one twin has allergies, and the other does not.

“What is it about the twin not affected that we can use for preventative measures in the general public?” she said.

Studying twins’ genetics not only benefits medical research, but it also influences many other fields of study. “Political scientists can use twins to understand if there’s a genetic influence on political affiliation and political investment,” Segal said. “And people interested in religious studies have used twins to understand whether or not there’s a genetic component to religiosity.”

The amount of interdisciplinary knowledge that we can learn by studying twins is vast, but we still have not figured out one of the most basic things about identical twins: how they are formed.

“We really don’t know what causes the fertilized egg to split. Why it divides sometime in the first two weeks is an absolute mystery,” Segal said.

Twins reared apart (often adopted just after birth) have been found to have similar intelligence levels, personalities and talents, which seems to indicate that genes are incredibly powerful. So does parenting really matter all that much? If a child’s genes can make them inclined to a certain behavior or talent, how powerful is parental influence?

Segal stresses that even though genetics are significant, twin studies reveal that the environment we are brought up in still plays a part in shaping who we become.

“Genes work in probabilistic ways — they make things more likely. They don’t make things absolutely sure to happen,” she explained. “And so if a child is mathematically inclined, well, the child needs support, the child needs books, the child needs opportunities to practice that skill. Without those, the child may not develop. So I think those are very, very important things to keep in mind when we think of the role of mothers and fathers,” she said.

Hannah Uebele is an intern at Innovation Hub.