What the Study of Twins Says About Identity
There are few things more compelling to watch than two identical twins sharing a meal. I had this good fortune a few years back at a restaurant in New York City and, while these identical twins were not matching in identical chiffon dresses, they were fascinating to watch – so much so that I nearly lost all sense of my social graces. But I am not alone in my curiosity regarding twins. The subject of twins is a compelling one for scientist, behaviorists, artists, writers, and for just the plain curious. What is it about twins, especially identical twins that enchant us so? Does the study of twins reveal key truths about happiness, intelligence, human nature and how our environment ultimately shapes us?
A recent article in National Geographic (with a series of fantastic accompanying photographs by Martin Schoeller) takes a somewhat long and hard look at identical twins in particular and how nature and nurture factor into the forming of a particular human being. The philosopher John Locke firmly believed that almost all of human personality traits could be linked to environmental influences and that each person was a tabula rasa (blank slate) whereas other behaviorists believe that the influence of heredity plays the most major role in forming who we are. Consider for a moment the following anecdote, lifted from the National Geographic article, illustrating the undeniable influence of heredity:
“The story began with the much publicized case of two brothers, both named Jim. Born in Piqua, Ohio, in 1939, Jim Springer and Jim Lewis were put up for adoption as babies and raised by different couples, who happened to give them the same first name. When Jim Springer reconnected with his brother at age 39 in 1979, they uncovered a string of other similarities and coincidences. Both men were six feet tall and weighed 180 pounds. Growing up, they’d both had dogs named Toy and taken family vacations in St. Pete Beach in Florida. As young men, they’d both married women named Linda, and then divorced them. Their second wives were both named Betty. They named their sons James Alan and James Allan. They’d both served as part-time sheriffs, enjoyed home carpentry projects, suffered severe headaches, smoked Salem cigarettes, and drank Miller Lite beer. Although they wore their hair differently—Jim Springer had bangs, while Jim Lewis combed his hair straight back—they had the same crooked smile, their voices were indistinguishable, and they both admitted to leaving love notes around the house for their wives.”
The word uncanny comes to mind. The fact is, the study of twins offers a precious opportunity to untangle the influence of genes and the environment—of nature and nurture. Because identical twins come from a single fertilized egg that splits in two, they share virtually the same genetic code. But studies, like the ones profiled in the above article, reveal that nature and nurture are not the only elements in play here. Some posit the notion that there is a third factor (or maybe fourth factor) that may exert influence and draw over who we ultimately become. There exists the study of epigenetics, which looks at how environmental factors can influence, and even alter, the way our genes are expressed.
As one could predict, the jury is still out on whether nature trumps nurture in the case of twins (I say nature has more of an edge) but the study of twins (even in the most casual of respects) will, no doubt, provide some illumination and perspective on these age-old questions.
*(photo by Martin Schoeller)