Why Are the Stories of Twins Switched at Birth So Amazing?

Life histories and findings from doubly exchanged pairs

Posted May 31, 2018

There have been just nine documented cases of twins switched at birth.

The most recent are pairs eight and nine, from Colombia. These two identical male pairs came to my attention in the fall of 2014 and I immediately knew that I wanted to visit them and study them. They are unique even among the previous seven because they are the only adult identical twins who were separated as infants in two-way exchange. Many details of their accidental switching are unclear, but what is known is that one pair was born in the capital city of Bogotá and the other pair was born in a tiny farming area near the city of Vélez, located about 150 miles to the north. (However, the family actually lived in a remote rural area called Vereda El Recreo.)

One of the newborn twins in the rural area was very ill, so his grandmother brought him to Bogotá’s better equipped hospital when he was just one day old. It was arranged for an aunt who lived there to return the baby to his family one week later. Perhaps because of the crowded nursery conditions and/or overworked nurses, this twin baby was exchanged with a twin baby in the other pair. Consequently, two sets of unrelated brothers grew up together for 25 years, believing that they were fraternal twins. Even their families believed this. If not for a young woman who one day mistook the identical twin she did not know for the one that she did knew, the truth might never have been known. These events propelled me to write Accidental Brothers: The Story of Twins Exchanged at Birth and the Power of Nature and Nurture.

Everyone is drawn to stories of twins. Perhaps that is because their matched behaviors and identical features pose intriguing challenges to expectations of individual differences. More importantly, people are eager to learn the extent to which their interests, talents and habits are shaped by genetic and environmental factors. Furthermore, it seems natural that twins should grow up together—so we are saddened to hear about twins who were separated and moved when we hear about their reunions.

The discovery of the switch occurred when the two pairs of identical twins were 25, a time when these young men were thinking seriously about career plans and personal goals. Events surrounding the discovery of the switch unfolded like the finest of spy novels. They show what can happen when friends confuse one twin for another, arousing their curiosity over the origins of these uncanny lookalikes. Not wishing to meddle in family relations, the young woman and her friend restrained their urge to know more. But they kept peeking at pictures posted on websites and asking questions until what they learned made silence impossible.  

Nancy L. Segal
Source: Nancy L. Segal

The Bogotá twins were perfect subjects for scientific study, which is why I went to South America with my collaborator Yesika Montoya, who told me about them. Twins are natural living laboratories, giving us windows into the way we are and how we got that way. People love to debate the relative contributions of genes and environments to intelligence, personality and talent, but they have only to look to twins to settle their arguments. The twin design is simple yet elegant, capitalizing on the genetic difference between identical and fraternal twin pairs. Identical twins share 100% of their genes, while fraternal twins share, on average, 50% of their genes, just like ordinary siblings. If identical twins are more alike in mathematics, sociability or life style than fraternal twins—and hundreds of studies show that they are—this means that genes are making a difference. 

The Bogotá twins are young and ambitious, energized and excited. Their lives have been completely revised by discovering that they grew up with an accidental sibling.