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  With all the bona fide scientific minds grappling with the separated twin similarities, it perhaps debases the argument to even mention one ersatz effort to explain these phenomena in a genes-free way: astrology. Because identical behaviors in people who share a birth date seem grist for the astrological mills, the astral possibility is put forward with distressing frequency, which is perhaps not surprising in a country where 46 percent of people polled in 1994 by Lou Harris for New York’s American Museum of Natural History did not believe in evolution.

  Fortunately the notion can be disposed of as quickly as it deserves. To be sure, identical twins are born at the same time, but so are fraternal twins. Yet identicals consistently measure closer in personality and behavior than fraternals. Whether Venus is rising, setting, or just standing still, the stellar configuration is the same for both types of twins, but they are very different in the degree of shared traits. The MZA similarities and the DZT differences could, in fact, be cited as evidence of astrology’s speciousness.

  In the same struggle to find nongenetic explanations to twin parallels, some point to the anecdotes about telepathic communication between twins. If twins can communicate telepathically, the suggestion is, this might consciously or unconsciously lead to both wearing the same four-pocketed shirt or both fearing the ocean. To test this possibility, Minnesota psychologist David Lykken ran a series of experiments. Like others who have conducted searches for signs of telepathy between twin pairs, Lykken could find none. Then too, it is never explained how such communicative power might lead a set of twins to check the same boxes on a personality-assessment questionnaire or, for that matter, why two twins communicating regularly over the psychic airwaves would agree to falsely claim a fear of heights or arrange to wear the same dress at their first meeting. Among nontwin females, more mundane means of communication like the telephone are usually used for the opposite purpose.

  As the number of these unforeseen parallels grew with each new set of twins, Bouchard and his colleagues became aware that capricious nature had presented them with a tricky public relations problem. Their dilemma was that of a hypothetical astronomer, a serious scientist to his bones, who spends his night scanning the moons of Jupiter with a powerful new telescope and, to his horror, discovers a McDonald’s arch peeking over a ridge on Io. What does he do? Announce his discovery and hope to God someone else sees it too? Or quietly pretend he never saw it?

  Judging from the Minnesota team’s experience, the latter course would probably be more prudent. The press reveled in the twin oddities to the same degree scientists scoffed at them. By the time the Minnesota team realized the public relations pitfalls, however, much damage had been done, as mentioned earlier, and the opponents regaled themselves with derisive comments to reporters about the ludicrous twin similarities. Since it was too late to deny having seen the McDonald’s arch, Bouchard’s reaction was to put a halt to press leaks.

  One example of this downplaying was Bouchard’s “explanation” of the two women who emerged from their respective jet planes wearing seven rings each. This was not so astounding, Bouchard reasoned; both sisters were proud of their long slender fingers and graceful hands, so it was only natural that they would adorn their physical asset with attention-getting jewelry. His aim was clear: Who would deny a genetic basis for slender fingers and well-formed hands? Further minimizing the coincidence, Bouchard pointed out that both women had flamboyant personalities plus the affluence to indulge this characteristic with enhancements like jewelry.

  Another example would be when Jack Yufe noted that his twin had exactly the same walk. Bouchard said this was not surprising in that they both had long torsos and short legs, traits that might affect a walk and traits few would deny have a genetic basis. Such sheepish rationales would become Minnesota’s standard reaction to the bizarre parallels: a somewhat apologetic “broadening out” of the highly specific phenomena to generalized, easier-to-swallow genetic expressions shared by twins that might have led to coincidences or would have at least lowered the odds from the McDonald’s-on-Io level. After all, the alternative was too grotesque to contemplate: the possibility of a gene for wearing seven rings, not six or five, but seven. What a hearty laugh the environmentalist gang at Harvard could have over that!

  But with similar phenomena arriving in the Minnesota labs with alarming frequency, damage control was in the air. Bouchard and his colleagues began playing up the MZAs’ differences. While they undoubtedly found them interesting, the emphasis was surely part of the effort to counteract the seeming preoccupation with oddball similarities. Bouchard even went so far as to state that twin differences might turn out to be more interesting than the similarities. “If one twin has schizophrenia and the other doesn’t,” Bouchard wrote in a paper, “the reason, if we can find it, might point to a cure.”

  And to be sure there were many differences among the Minnesota twins, physical ones as well as in personality. A pair of Japanese-American women, raised separately in California, were so unlike in appearance that they were assumed to be fraternal; only blood tests proved them identical. They were also quite different in personality; one was friendly and outgoing, the other quiet and reserved. One had a phobia about flying, the other had no such fear. At the same time there were marked similarities, mostly physiological, but one right up there in the strangeness big leagues: They both had a cracked toenail on the same toe. Also, both had had miscarriages and both suffered from the same intestinal ailment.

  Oskar Stohr suffered from narcolepsy, while his twin, Jack Yufe, did not. A number of twins had been bed-wetters as children, while their twin had no such history. In five pairs, one twin had neurotic symptoms, such as depression, that had been strong enough to require medication. The other twin was symptom free, or the symptoms were significantly weaker. It was not unusual to find one twin with a phobia the other did not share. One of two male twins in their twenties had a strong dislike for smoking; his brother smoked regularly. With the generally high heritability trait of I.Q., three pairs measured close to twenty points apart. Since the identical twins had exactly the same DNA, the many differences between them, including physiological ones, had to be environmental. The environment appeared to be alive and well.

  That there were differences between MZAs merely says that identical twins reared apart or reared together do not share all traits and qualities, a hypothesis advanced by no one, certainly no one in the Minnesota group. Such environmentally induced inconsistencies take little away from the potential genetic significance of the identical habits and quirks found in both twins. In addition, pronounced differences in MZAs were the exception, not the rule, in Minnesota. Of the twins discordant for various traits, most shared a longer list of similarities. While many of the reared-together fraternal twins shared no noteworthy traits, of the seventy-odd sets of MZAs examined by the early 1990s, over half had at least three such odd parallels, a fact that defied probability laws of coincidence.

  But it is not a matter of keeping score. The mirrored behaviors were never presented as scientific data and only leaked out because they were so surprising. For observers with no stake in the genes-environment sweepstakes, the parallels demonstrated that the genome, in certain situations, seems able to manifest itself in remarkably specific ways. To some, a number of the bizarre matches could stand by themselves as challenges to existing thinking on the limits of genetic governance.

  The utility of the identical behaviors in MZAs was not just their power to broaden thinking about gene penetration. They promised more specific benefits as well. One example was the migraine headaches of the Jim twins. Not only did both men suffer from them; they did so at the same time. Their migraines had started at the same age, stopped after the same number of years, started again at the same time, then stopped for both of them—for good, it appears. According to Bouchard, “physicians had never thought such a complicated migraine pattern could be under genetic control, but now they are looking out for other signs of it.”
r />   1The problem with the term lies in the stipulation within a given population. If the trait measured was dark hair and the group was Iraqi males, there would be no variation and the heritability would be zero. If the group measured were U.N. employees, the variation would be large; and because this is a gene-based trait, the heritability figure would be close to 100 percent. Heritability, therefore, is completely dependent on the group measured. The hateful result is that you can have a heritability of zero in a trait that is 100 percent genetic. For a nongeneticist like me, this knocks the English language senseless.

  SEVEN

  MORE WEIRDNESS

  SIGMUND FREUD WAS remarkably successful in persuading the world that another level of mental activity, the subconscious, was a wellspring of many of our thoughts and actions. The fake sneezes of Oskar and Jack, the tree benches of the Jim twins, and a hundred other examples of replicated behavior strongly suggest another possibility: a genetic nudge toward a particular action at a particular time. This is a concept similar to Freud’s in that it speaks of a force other than pure consciousness that is guiding and influencing our decisions. The difference is that the twin parallels suggest that one source for our decisions and actions may not be a repressed childhood desire or conflict but is linked instead to an infinitesimal bit of nucleic acid in our DNA. As a theory, this is at once simpler; but in its mechanistic slant on behavior, it is far less palatable than Freud’s. It is certainly less poetic.

  Because the mirrored-behavior anecdotes do significant damage to existing notions of human function, they inevitably meet with strong resistance. Research hoaxes or journalistic exaggerations are a lot more digestible than alarmingly mysterious processes going on inside us all and threatening our sovereignty over ourselves. The former is an old story, the latter disturbingly new. And because these phenomena are so vivid and evoke a far narrower focus of genetic prods to behavior than previously imagined, they are resisted even more vehemently by the radical environmentalists.

  Although the coincidence explanation could not be eliminated empirically, it becomes a statistical absurdity in light of the sheer number of matching traits within given sets of twin pairs. The example is often cited that in a group of twenty-four random people, there is a high probability that two will have the same birthday. The example only works to dismiss twin parallels, however, if the claim can be made that the pair sharing birthdays also had the same profession, the same breed of dog, the same favorite actor, and on and on.

  In efforts to discredit the parallels, critics take an example in isolation and weigh the likelihood of coincidence. But this does not address the phenomena. No one suggests that twin males drinking the same brand of beer is a remarkable coincidence, but the critics still point to the popularity of that particular beer, the small number of mass-market brands, and so on. Although some of the matching behaviors by themselves are quite striking, it is the aggregate within a given pair that is so telling. In the case of the beer drinkers (twins who were both bachelor firemen), the next item on their similarity list was that they both drank their beer with a little finger crooked under the can. The same beer meant nothing, drinking from a can meant nothing, but the little finger under the can—and about fifteen other identical quirks this pair shared—tends to rule out coincidence.

  Another effort to dismiss the phenomena argues that if you sit any two people down and ask them to look for parallels in their lives, they will inevitably come up with a few. One fact emerged from the Minnesota research that handily disproves this imaginative conjecture and makes unnecessary belaboring the large number of parallels in single twin sets. All the fraternal twins were invited to look for such similarities, to search their pasts, their foibles, their likes and dislikes, to find matching behaviors. Only one set was able to do so. None of the others was able to come up with one example of the sort of precisely replicated behavior that marked the separated identical twins, although fraternal twins share roughly 50 percent of their genes. It is idle to suppose that the two random individuals the critics postulate, who share none, would do better in a search for coincidences.

  Future research and new methodologies will be needed to nail down the precise scientific significance of the matching-behavior phenomena; but they are there, and they have been recorded. It is now the job of the scientifically curious to push for an explanation of how the McDonald’s arch came to be on a moon of Jupiter. An opportunity for exciting new knowledge could be lost by those who stubbornly insist the arch is not there simply because the apparition does not conform to preexisting ideas of the way things are.

  Most scientists acknowledge how frequently new knowledge is developed by colleagues following their hunches into specific and sometimes elaborate experimental tests. If after endless experimentation, and after successful replications by others, a theory is confirmed, the success can owe as much to the inspirational hunch as to the laborious experiments. Whatever else the twin parallels may be, they provide rich material for hunches.

  WITH SO MUCH outside attention being given the strange twin similarities, Bouchard repeatedly emphasized that his study was about heritability mean figures of concordance and not about duplicated behavior between specific twins. Even so, one of Minnesota’s first reared-apart-twin papers had striking examples of these phenomena. In spite of the random selection of the study’s twins, several of them suffered from psychiatric disorders. Of the afflictions, a surprisingly high number were shared by both reared-apart twins. When Bouchard and some colleagues were invited to a conference in Israel on genetic aspects of psychiatric problems, they felt that the twin pairs they had studied so far demonstrated significant correlation patterns of disturbances. They summarized their findings in a report to the conference.

  The paper was based on fifteen pairs of MZAs; all except one pair had been separated within six weeks of birth. Among the similarities, two female pairs and two male pairs had speech impediments. In four of the fifteen pairs both twins had a phobia of heights, while in two other pairs just one of the twins had this fear. When both twins had a phobia, it was not always the same phobia; but in one pair it was remarkably so.

  Two thirty-five-year-old British women, raised in different families and not meeting until they were in their thirties, had a strong fear of water. This presented a special problem for the two women, as their families frequently went to the beach in warm weather. On these outings both women felt obliged to join the others for ocean dips and had devised an odd way of dealing with their water phobia. Each of them managed to get their feet wet by backing into the sea very slowly. In both cases they would proceed in this way until the water reached their knees, at which point neither could go further. It is interesting to consider the respectful hearing most educated people would have given a psychotherapist had he or she traced the water phobia of one of the Englishwomen back to a childhood trauma.

  Perhaps no reared-apart twin parallel was more specific than a dream that a pair of middle-aged American women both experienced years before they met. The twins also shared more routine disorders. As children, both were bed-wetters, the problem ending for both when they were twelve. As adults, but before being reunited, both had had problems with emotional stability, had abused amphetamines, and had periods of intense depression. Most striking of all, while they were still teenagers, both had had the same recurring nightmare: They felt they were suffocating because their mouths were stuffed with doorknobs, needles, and fishhooks.

  While dream analysis is less popular with Freudian analysts than it once was, it would still be instructive to round up a group of the remaining specialists in this therapeutic device, tell them about the two women, then ask each to analyze the dream. Some analysts would surely sidestep the trap, but perhaps others might jump in. (The differences in the responses might in themselves prove interesting, which is one reason why psychoanalysts would never participate in such an analytic bake-off.) It would be a splendid test of the therapists’ resourcefulness if, after they had presented
their analyses of one woman’s fishhook dream, they were asked to explain that the dreamer’s twin sister, growing up separately, had the identical dream.

  AMONG THE LONG LIST of matched behaviors in reared-apart twins, many of the most striking involve proper names—the two Jims naming their dogs Toy and their sons variations on James Alan; Dorothy and Bridget having daughters both named Louise; and so on. Among the twin parallels in the 1937 reared-apart twin study of Newman, Freeman, and Holzinger, one rivals any turned up by Bouchard’s group. Two middle-aged male identical twins, separated for a good portion of their lives, both worked as telephone linemen and had wirehaired fox terriers named Trixie.

  When attempted explanations appear too preposterous, there is a natural tendency to reject them testily and strain for more reasonable explanations. With duplications of names for children and pets, a genetic rationale is so far-fetched, critics point somewhat desperately to fashions in names that could lower the coincidence odds. Indeed, as for the breed, at the time of Newman’s research, wirehaired fox terriers were one of the most popular dogs in America. If both twins had merely chosen fox terriers, the parallel would have been mild. But for each twin to affix the never-fashionable name “Trixie” to their terriers renders the fashion explanation unsatisfying.