Will & I by Clay Byars

Author:Clay Byars
Language: eng
Format: epub
ISBN: 9780374714833
Publisher: Farrar, Straus and Giroux

15

Will uses primarily his left hand, by habit, but he’s almost completely ambidextrous. He plays tennis left-handed, but he writes and plays Ping-Pong with his right. He can switch his dominant hand with relative ease, especially in tennis, something I was never able to do. Once, when his collarbone was broken, he beat Caldwell 6–0 while playing right-handed (and in dress shoes). For the first twenty years of our lives, that had been the only physical difference between us, apart from the hole in his heart, which no one could see. We were still the same internally in so many ways, I knew. But now we looked very different. Our twinship had been altered.

The kind of twins Will and I are—male-male monozygotic (two identical boys)—is the rarest form of twinship, statistically. There are more likely to be fraternal (or sororal) twins than identical, and there are more likely to be female identical than male identical. It’s also true that male-male identicals possess the highest overall degree of DNA overlap. We are the most identical. The reasons for these differences are poorly understood even by the scientists (just as we don’t understand why a certain tribe in Africa, the Yoruba, has an astronomically high twin rate—although in that case it may have something to do with a certain type of yam they eat). It’s accepted as a myth in the medical community that twins run in families, although there are plenty of examples to give the myth credibility. My uncle, my father’s older brother, had two sets of twins.

I wrote that ours is “the rarest form of twinship,” but that should be changed to “the rarest form of relatively common twinship.” There are some extreme forms. Apart from conjoined twins—identicals born with their bodies fused—there are parasitic twins, where one twin dies in the womb and its body disappears into the other (often to reappear alarmingly later in life, in X-rays). There are also chimeric twins, where one twin disappears into the other but continues to live. This condition was discovered when doctors found that a woman did not share the DNA of a child she’d given birth to. It turned out that her lost twin’s womb had nurtured the baby. There exist “mirror image” twins, those who for unknown causes split apart later in the gestation process (a week after conception, say) and who, although they look alike, will possess curious asymmetric tendencies, opposite-handedness, the same birthmarks but on different sides of the body, even dramatically opposite temperaments. Finally, there are, weirdest of all, the varieties of “semi-identical” twins. These are twins who share their mother’s genes while each having the genes of a different father. It happens most frequently through a process known as superfecundation—the mother releases two eggs, and both get fertilized, at different times, by different men—but there’s another scenario, the weirdest of the weird, called sesquizygotism, which occurs when two sperm cells fertilize one egg, forming a curious three-part creature, a “triploid,” which then splits apart.

Here’s what I find interesting about monozygotism, the kind of twinship Will and I possess.

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