The mystery of identical twins is one that has long baffled theorists. How can two people have identical genes in every cell of their body and look so alike that people can hardly tell them apart, yet be so completely different in their personality and behavior?
Like ordinary siblings, parents will tell you that, for those who know them well, their identical twin children are as different as night and day. The plain truth is that no matter how much they may look alike on the outside, identical twins are almost never the same in personality and behavior. In fact, most often they are diametric opposites.
These differences are most stark in some astounding cases, such as when one identical twin, who carries the same DNA, becomes a criminal while the other is an honest, law-abiding citizen. Or when one twin is distinctly heterosexual while the other is a confirmed homosexual. One case I cited in my book is that of a pair of Siamese twins in the 1800’s, Chang and Eng, who were conjoined at the hip, but whose personalities and behavior were diametrically opposite. Even though they became wealthy plantation owners, one of them smoked, drank, hung out in bars, sought out wanton women and followed all the vices of the 1800’s, the other was straight-laced, well-mannered, well behaved and an upstanding, model citizen.
Numerous research studies have been done in an effort to explain the reasons behind these differences. The movie “Three Identical Strangers” illustrates the extreme alienation between a set of identical triplets who were separated at birth and reared apart, but came to know each other during adolescence. It was a failed experiment that sought to research the age-old dilemma of nature vs. nurture.
An example from the Dr. Phil show told of a set of 8-year-old identical triplet boys whose ambitions were widely varied. One wanted to be a sportsman, and decorated his room with everything he could find about sports. A second brother aimed to join the military and collected as many military souvenirs as he could. The third had the ambition to become a girl, and this child did everything he could to emulate the female gender, including painting his nails, coloring his hair, putting on make-up and decorating his room in pink. To ask how this could happen if DNA were the sole determinant of personality and behavior is a fair question.