This is a fascinating article. It's about two pairs of identical twins where one twin in each pairing was swopped for a twin in the other pairing, so that each twin grew up as one of apparently fraternal twins. Lily Tomlin and Dolly Parton played out this scenario in a movie (can't remember its name).
But there's more to the article than the individual lives of the four men in it. Read about the epigenetic findings towards the end of the article, while remembering that much of this field is still in its baby clothes:
Before starting her research, Segal would not have been surprised if each young man tested similarly to his identical twin, despite their different environments. But her preliminary results, she said, show that on a number of traits, the identical twins were less alike than she initially anticipated. ‘‘I came away with a real respect for the effect of an extremely different environment,’’ Segal said.
Craig has analyzed the epigenetic profiles of 34 identical and fraternal twins at birth, collecting swabs from their inner cheeks. To Craig, it was noteworthy that in some cases — not many, but some — the epigenetic profile of one newborn twin was more similar to an unrelated baby than to the identical twin with whom that baby shared a womb. Structural differences in the womb could possibly account for it, Craig says — a thicker umbilical cord for one than the other (there are, in fact, two cords) or an awkward site of connection for the umbilical cord on the placenta. But he recognizes that there could be additional factors still in the realm of guesswork. Perhaps one twin is farther from the sound of the mother’s heart, its reassuring steady beat, sending that child on a slightly different life course.
It's that possible dance between what used to be called nature and nurture which fascinates me. To the extent the new field of epigenetics holds up its promise, our understanding of what is innate and what is environmental may be changing so much that many of our current debates (about gender, say) will sound silly in the future.