You’re traveling through another dimension—a dimension not only of sight and sound but of mind. A journey into a wondrous land whose boundaries are that of imagination … a land of both shadow and substance, of things and ideas.
—Rod Serling
As a child, I loved this magical introduction to the weekly television show The Twilight Zone, whose episodes portrayed ordinary people in extraordinary circumstances. Each thirty-minute episode blended science fiction, high suspense, and great drama, giving viewers a fanciful white-knuckle ride through exotic places with infinite unforeseen possibilities. The current stream of online and on-air reruns attests to the show’s universal and enduring popularity.
The story of the switched Colombian brothers could be an episode from that series. From the twins’ perspective the discovery was a sudden and unexpected rewrite of their life histories, a complete revision of their childhood memories and the heartbreaking business of squaring opportunities lost with opportunities gained. Studying their experience and its aftermath also promised an adrenaline-charged ride for me, a journey to a new land to hopefully meet a type of foursome that no researcher had ever encountered. Without doubt, these brothers would leave an indelible mark on our understanding of how interactions between genes and environments affect our abilities, job choices, eating habits, and physical strength. Events in the twins’ lives would also expand knowledge of how new mothers know who their babies are, the status of legal procedures and rulings regarding switched-at-birth infants, and the emotional impact of finding out that you are living someone else’s life.
Questions Without Answers
The only information about the Colombian twins came from Caracol TV’s two-part series produced by Séptimo Día, a 60 Minutes–style newsmagazine that told the story to the people of Colombia and the adjacent nations of Ecuador and Venezuela.1 The report, “Crossed Lives,” was not broadcast widely, although Yesika, who is from Bogotá, saw it when it first aired in October 2014. She knew of my previous work on switched-at-birth twins and emailed to see if I was interested in this case—I was!—and we soon agreed to work together on one of the most fascinating projects either of us could have imagined.2 My research experience with reared-apart and switched-at-birth twins in Minnesota and elsewhere had taught me what information we would need from the twins and the types of interviews we would use and questionnaires we would administer. Yesika’s social work training and professional associates in Bogotá would facilitate contacts and interactions with the twins and their families, as well as meetings with the psychological examiners, geneticists, hospital staff, and attorneys we hoped to visit. We also hoped to write a series of scientific articles and a book that would describe the findings and events that so radically changed the life histories of four young men.
It turned out that William, assisted by his then girlfriend, who had some television contacts, was responsible for bringing the twins’ story to the media; he called every department at Caracol TV until he found the right one. Jorge was enthusiastic about his twin’s idea, but Carlos and Wilber were not. Carlos had strong reservations about involving the media, concerned that he would lose control of what was aired, and he was largely correct. “Some TV people wanted me to act really sad, do this, do that, act like I was depressed and really exaggerate my feelings. I dislike sensationalism,” Carlos said. Jorge also has his limits; he did not want to be “turned into a clown,” but he was eager to share his story with the world. Each brother’s reared-apart twin held attitudes about public attention that aligned perfectly with his own. Nevertheless, Carlos and Wilber, while reluctant, agreed to go along, most likely because of Séptimo Día’s offer of free DNA testing, a costly but vital step toward confirming beyond a doubt that a baby exchange had occurred. Everyone had to know because their life histories, personal identities, and family relations hung in the balance.
* * *
How the exchange of babies actually happened was the great unanswered question, just as it was in the seven other cases of switched-at-birth twins I have known. These mysteries are rarely solved, so imagination and speculation run wild. We learned that babies like the four twins, born prematurely at seven to eight months, were routinely placed together on a large table in the newborn nursery of the Bogotá hospital, so perhaps William was lying closer to Wilber than to Jorge, and a staff member forgot which twins belonged together. Or perhaps an overworked assistant misread the babies’ identification tags, or maybe the tags fell from their wrists and were incorrectly reattached.
Séptimo Día producers dramatized these possibilities when they filmed part of the report in the baby nursery of the Bogotá hospital where one set of twins was born. Two incubators were positioned several feet from each other, each with a pair of infant twin dolls dressed in striped pajamas and matching caps with small white ears protruding from the top, giving the impression of tiny bears. The incubator on the left held the La Paz pair dressed in blue, the one on the right held the Bogotá pair dressed in purple, and each twin doll had a different name emblazoned across his belly. The narrator walks toward the incubator on the left, removes Carlos, and brings him to the incubator on the right, placing him between Jorge and William. Moments later he picks up William and delivers him to the incubator on the left, setting him next to Wilber. Then we see the four adult twins sitting alone, slumped between incubators and looking forlorn. Of course, this was all done for effect because no one really knows what happened in the nursery a quarter of a century ago. This imaginary scene embodied all that Carlos disliked about media attention and Jorge’s cautious, but less intense, reservations.
Despite this dramatic depiction, or perhaps because of it, many new questions arose. Did the exchange of babies happen on the day the baby from La Paz arrived in Bogotá or later in the week? And why didn’t his grandmother notice the difference between the baby she brought to Bogotá and the one that came back to La Paz? Or perhaps the nurses were tipsy, as one of the twins’ aunts truly believed.
None of these hypotheticals and unknowns was as haunting as the statements made by Gilma Ospina, a nurse who appeared on the program and had worked in the premature care unit in 1988, the year the twins were born. She acknowledged that she could have inadvertently switched two of the twins, but she did not feel the need to apologize for such a mistake because no one can know whether she was truly responsible. She speculated that the two babies’ identification tags, just simple pieces of tape, had fallen off and were incorrectly reattached. Even if she had misplaced the babies, she was happy to see that the switched twins were doing so well as adults.
The program also equated Jorge and Carlos’s city life with wealth and opportunity, and William and Wilber’s country life with poverty and deprivation. It made for a great television story, but a crucial aspect of the difference in their childhood environments is easy to miss. In terms of material possessions and necessities of life, both sets of accidental brothers did differ—except that each pair believed they were living in homes comparable to others in their area. Both families worked hard to maintain the standard of living they had set for themselves, and both families were successful in that respect.
Turning to science, Séptimo Día interviewed the geneticist Dr. Emilio J. Yunis of Bogotá, whose Institute of Genetics performed the DNA analyses. Yunis was stunned by the striking physical resemblance of each reunited set of twins, half-seriously suggesting that a DNA test was probably not necessary. But the seriousness of the twins’ expressions as they listened to the results reminded viewers of the far-reaching implications of this news for the twins and their families.
Tracking Down the Twins
Séptimo Día included a short interview with the Colombian attorney Francisco Bernate, who was not officially involved in the case but was prepared to offer an opinion.3 We never met him, but on-screen he looked professorial in a gray jacket and purple tie with his long dark hair swept back from his face. He commented first on the slim possibility of the twins’ receiving compensation from the hospital where the switch had taken place; he believed this was unlikely because more than twenty-five years had passed since the mistake was made. He opined that the damage began when the truth was first known, asserting that everyone has a right to their identity and to know where they have come from.
We had been unsuccessful in trying to reach the twins because we were unable to find the twins’ phone numbers, contact the TV show producers, or find additional information online. But we realized Bernate could connect us and after weeks of waiting he did. It helped that Bernate was a professor of criminal law at the Universidad del Rosario’s law school, where Yesika’s sister, Alexandra Montoya, who is famous for her impressions of Colombian celebrities, was working toward her second career. This personal connection probably was responsible for the lawyer’s email message to Yesika that included Jorge’s email address and cell phone number.
Yesika and I were now on an exciting journey together, with the dual goals of finding the four brothers and convincing them to participate in the first-ever research on doubly exchanged adult twins. By the end of December Yesika had flown to Bogotá for the holidays and met with three of the four twins; Wilber was unable to attend because he was covering the butcher shop. The three young men and Yesika discussed research plans, when they might be available to us, and a little more about their getting to know one another. Later I received a photo that showed Yesika and the three twins seated around a table, as well as a little boy who was cuddling up to Jorge. That was Santi, Jorge’s then four-and-a-half-year-old son, whose mother was Jorge’s former girlfriend. The recently reunited twins Jorge and William were seated together, while Jorge’s accidental brother, Carlos, sat apart.
For two tense months, October to December, we waited to find out whether the twins would meet with us. But as 2015 approached, Jorge told us we would be welcome in Bogotá. We arranged for a ten-day stay in Bogotá in late March and early April, including a one-day trip to La Paz. Information gleaned from doubly exchanged twins, especially those raised in such contrasting environments, would be a unique addition to the rich history (since 1922) of reports, articles, and books about reared-apart twins, as well as to my own ongoing research about reared-apart Chinese twins and other separated pairs.4 The first mention of twins reared apart was not in the scientific literature, but in a play by the Roman comic dramatist Plautus (254–184 BC), The Menaechemi (The Twin Brothers), a hilarious tale of separated twins, mistaken identity, and widespread confusion.5
Twin-Family Relations
Seeing the photo of the twins and Santi suggested to me that William, Jorge’s identical twin, might be rejoicing at the sudden acquisition of a nephew. In fact, he is Santi’s genetic father as well as his uncle, because William’s biological relationship to Santi is exactly the same as Jorge’s. Parents transmit half their genes to each child; because identical twins share 100 percent of their genes, either twin could have fathered little Santi. Until recently genetic testing was unable to distinguish an identical twin father from an identical twin uncle, but in 2014 German investigators figured out how to do this. If one twin develops a mutation after birth it could be passed down to his child, and since the other twin would not have that mutation he could not be the father.6 This technique would be handy in cases of disputed paternity in which both twins had sexual relations with the same woman and she became pregnant or if a twin was suspected of having an affair with his brother’s wife. Before 2014 judges were powerless to assign responsibility for child support in such cases, but now they can because ten to forty mutations can be expected in each paternal generation.7
An array of other curious relationships emerges when identical twins raise families. When William has kids, they will be cousins to Jorge’s kids, but all the children will have a genetically identical parent. This quirk of birth transforms close cousins into genetic half-siblings, who share an average of 25 percent of their genes, whereas ordinary first cousins share just 12.5 percent. Family relationships grow even stronger when identical twins marry identical twins because all four spouses turn into the genetic parents of their nieces and nephews. In one such family that I know the wives became pregnant at the same time and delivered their children on the same day, changing these legal first cousins into the equivalent of genetic fraternal twins.8
Not surprisingly, one of my ongoing studies shows that identical twin uncles and aunts feel socially closer to their nieces and nephews than do fraternal twin aunts and uncles. I suspect that behind those feelings are identical twins’ perceptions of the behavioral and physical similarities between themselves and their nieces and nephews. The growing field of evolutionary psychology adds an intriguing explanation: it makes sense to “be nice” to your close relatives as a way of getting your common genes into future generations, namely the concept called inclusive fitness. Of course, people do not make genetic calculations in their head as they go about their daily interactions, but they act as though they do.9 In contrast fraternal twin aunts and uncles share an average of 25 percent of their genes with their nieces and nephews, the same as in nontwin families. Thus, investigators would expect to find more variability in the nature of their perceptions of similarity and social closeness.
I wondered whether Jorge’s accidental brother, Carlos, was suddenly grieving the loss of a nephew he had loved for nearly five years, now that he was no longer the uncle he had thought he was. These were among the hard questions for which I hoped to find answers in Bogotá.
Transformers and Matryoshka Dolls
I occasionally teach a graduate-level seminar about twin research, and one of the exercises I assign students is to dream up an ideal experiment for figuring out the extent to which genes and environment affect our different traits. “Be creative,” I tell them. “Really stretch your mind and go beyond the classic twin study.” At this point in the course the students understand the logic of the classic twin study design, which involves comparing similarities of pairs of identical twins (who share 100 percent of their genes) and pairs of fraternal twins (who share an average of 50 percent of their genes). Greater resemblance between identical than fraternal twins in any trait, such as solving math problems, participating in sports events, or attending religious services, shows genetic influence on those behaviors.10 We find that genetic influence affects virtually every trait we have measured, but the environment also plays a role, affecting some behaviors more than others. For example, genetic factors more strongly influence general intelligence, accounting for 50 to 75 percent, whereas their influence is less on personality (50 percent), self-esteem (38 percent), and longevity (33 percent).11
Genetic and environmental influences work together to shape our behavioral and physical traits, and in the case of intelligence we can say that about 50 to 75 percent of the variation is associated with genetics and 25 to 50 percent is associated with the environment. It is impossible to divide the intellectual makeup of a single person into genetic and environmental components because they are completely intertwined within an individual.12
I have been pleased with my students’ proposals, but my favorite is a study of sets of same-sex triplets comprising an identical twin pair and a fraternal cotriplet. That trio poses a great natural experiment because all three triplets share the same environment, but only two share all their genes. If the identical twins are more temperamentally alike and socially closer to each other than to the fraternal member of the pack, this tells us that genetic factors influence our personality traits and friendship choices. Research using twins, who are far more plentiful in the population than triplets, shows exactly that.13
This triplet experiment can be extended even further. Let’s say that one identical twin was raised by the biological family, while the other identical twin and the fraternal cotriplet were raised together in an adoptive home. If researchers found that the separated identical twins were more alike than the reared-together nonidentical pair, this would show even more convincingly the genetic influence on the traits being measured. Researchers would need to study many of these rare sets to find definitive answers to nature-nurture questions, but even one case or a few can provide important insights that can be further explored in large-scale studies. When it comes to triplets’ social activities and relationships, identical partners generally align more closely with each other than they do with their fraternal ones. For example, my colleague’s triplet children, Mike and Mark love to indulge in overeating, whereas Matt is proud to not be a member of that culinary club.
None of my students’ ideas, or my earlier ones for that matter, came close to the exceptional research possibilities offered by the switched Colombian brothers. I began thinking of the four twins as Transformers, the popular toy that assumes different forms and features by manipulating its parts. The potential experimental contrasts the Colombian twins generated also reminded me of matryoshka dolls, the painted Russian figurines that fit inside one another in increasingly smaller sizes. I grabbed some paper from my printer and started mapping out the myriad relationships and comparisons that were possible.
Reared-Apart Twins, Virtual Twins—and the New Replicas
In mathematics a combination is a selection of a specific number of items (e.g., two people) from a larger number of items (e.g., four people) without attention to who comes first or second with respect to order. Higher-order multiple births—triplets, quadruplets, and more—are fun to work with in this regard. When thirty-three-year-old Nadya “Octomom” Suleman of southern California gave birth to octuplets in January 2009, I wrote a paper showing that her eight babies yielded twenty-eight unique twin pairs when they were organized into groups of two.14 The situation is even more amazing when we consider that Suleman had had six fertilized eggs implanted in her uterus and two of those eggs divided, producing two identical twin sets in the bunch.
I performed similar calculations for the four Colombian brothers and came up with three results, two that were not surprising and one that was completely unexpected and exciting. By pairing the brothers every way I could, I ended up with six distinct sets:
• Two identical reared-apart twin pairs, Jorge and William, and Carlos and Wilber. These pairs share their genes but did not share their environment.
• Two unrelated, or virtual twin, pairs: Jorge and Carlos, and William and Wilber. These pairs shared their environment but do not share their genes.
And for the first time in any study:
• Two replicas: Jorge and Wilber, and Carlos and William. These pairs share neither their genes nor their environment, but they replicate the unrelated, or virtual twin, pairs, who share only their environment.
* * *
Reared-apart twins are easy to define—they are twins separated at or soon after birth and raised by two different families. They are genetically identical, actually clones by definition, but because they do not share an environment, their behavioral and physical similarities are the result of their common genes. All of us can use this information to understand why we are the way we are and how we got that way. In addition, reared-apart identical twins give us direct estimates of how much genes matter, making these twins a cleaner, neater twin research design than twins reared together, whose shared experiences could enhance their similarities. No wonder reared-apart identical twin pairs have high status in the hierarchy of twin research methods.
However, despite some critics’ claims that most identical twins are alike because they are raised together and are treated alike, it would be incorrect to assume that they are alike because they were raised together. It would also be incorrect to suppose that increased contact between reunited reared-apart twins makes them alike. This has been shown repeatedly, but was revealed most dramatically by the first-ever personality study of four groups of twins that my Minnesota colleagues and I conducted in 1988. This project included identical twins reared apart, fraternal twins reared apart, identical twins reared together, and fraternal twins reared together. As expected, we found that the identical pairs were more alike than the fraternal pairs. The surprise was finding that identical reared-apart twins are as alike in personality as identical reared-together twins.15
This counterintuitive finding means that personality similarity between family members in traits like traditionalism and aggression come from their shared genes, not their shared environment. There is no other way to explain why separated twins like Lily and Gillian, who were scared of Santa Claus and clowns, dressed up as ballerinas at Halloween, why Samantha and Anaïs chew on their hair when they get nervous, why Bridget and Dorothy wear more rings and bracelets than anyone they know, or why Todd and Josh both identified as female and independently underwent surgical transformation to have their biological sex and gender identity align.16
Todd and Josh are the only known pair of separated identical twins who have experienced gender dysphoria (the persistent discontent with one’s birth or assigned gender and identification with the opposite gender) and have undergone surgery to change their sex. After their birth their forty-year-old mother was diagnosed with facial cancer so, following advice from various hospital staffers who believed that caring for more than one newborn would be too taxing, she placed one twin up for adoption. By the time the twins reunited at age fifteen, both felt uncomfortable living as males, had engaged in cross-dressing, and were apprehensive about developing secondary sex characteristics in adolescence. These twins make a powerful statement about genetic influences on transgenderism (the transient or continued identification with the gender that is different from one’s birth gender) and transsexuality (the social or surgical transition from male to female or female to male). Genetic effects on gender dysphoria are also shown by the finding that one-third of transsexual identical male twins have a transsexual twin brother, whereas no transsexual fraternal male twins have a twin who is also transsexual.17 Of course, environmental influences before and after birth also play a role because identical twins’ similarity is less than 100 percent.
It seems reasonable to attribute parent-child or brother-sister similarities to shared experience, but researchers cannot disentangle genes and environment when biological relatives live together. The only way to do this is to compare resemblance in kinships that are genetically and environmentally revealing, and the best pairs are twins raised together and apart. Upon doing this we find that environment matters nearly as much as genes when it comes to personality, but it is mostly the individual experiences that we do not share with our relatives, such as being mentored by an inspiring professor, taking an exotic vacation, losing assets in a Ponzi scheme, or being attacked by an unknown assailant, that influence our personality traits. However, nonshared experiences work in unpredictable ways—after being attacked, one person might be energized to improve public safety, whereas another might be too fearful to leave home.
By now scores of twin studies have shown that genes affect just about every human trait that anyone has ever measured. A curious exception is love styles—it seems that how quickly or slowly we fall in love with someone is mostly experiential in origin.18 However, the only twin study to look specifically at love styles was conducted nearly twenty-five years ago, and recent findings about the brains and personalities of people in love could make for great twin research. The anthropologist Helen Fisher, who is an identical twin, and her colleagues found that certain neural mechanisms are associated with mate attraction and mate choice, and that, based upon a personality questionnaire, people might be classified as one of four love types—negotiator, director, builder, or explorer—although the types overlap.19 Comparing the similarities and differences between identical and fraternal twins could reveal genetic influences on brain processes and personality traits that affect our love lives.
The wealth of genetic findings does not surprise me, perhaps because I shared my home environment with a fraternal twin sister who was, and still is, quite different from me in most respects. As children our preferred cereals were Rice Krispies and Kix, our favorite ice cream flavors were chocolate and coffee, and we rarely, if ever, sampled our sister’s choices. Our differences in eye color, height, and running speed were apparent from an early age, and I had fun seeing the surprised looks on people’s faces when I told them we were twins. I witnessed genetic effects before I knew what genes were.
* * *
Researchers have found other, more surprising results. Since the mid-1980s studies of adult twins, raised apart and together, have shown that genetic factors influence political perspectives, social attitudes, divorce tendencies, financial decision-making, and religious involvement, behaviors previously thought to reflect how our parents raised us.20 Earlier twin studies did not detect genetic effects on these behaviors because they studied children still living at home, under the thumbs of their families. But as children approach adolescence and adulthood, their actions, tendencies, and choices speak more clearly of their natural preferences. For this reason it is paradoxical, but true, that the older we get the more important our genes become. Most people are surprised to hear this because their logical mind says that as people age they accumulate a wealth of different experiences that should affect their behavior. But logic and reason do not replace what the data tell us: we become more selective about where we go and what we do as we get older, reflecting genetically based choices, some of which may be kicking in for the first time. Consistent with these findings is that adopted siblings who grew up together become less alike in general intelligence over time as genetic effects grow stronger in the environments they individually seek. That is because as people move from childhood to adolescence and beyond they gain freedom and choice over what they do and who they do it with, allowing their genetic predispositions greater expression.21
* * *
Two sets of unrelated, or virtual, twins are among the different pairs generated by the Bogotá brothers. I like the term virtual twins because it’s clever, timely, and fits the novel, twin-like pairing I first came across in 1990.22 I wish I had thought of this term myself, but it came from a smart mother who offered two such children for study. Virtual twins (the same-age, biologically unrelated individuals raised together soon after birth) should not be confused with so-called Irish twins, children born nine or ten months apart to the same parents. Virtual twins are much closer in age, and some are even born on the same day. Furthermore, they have no common genes, but Irish twins do.
Most virtual twin pairs are made up of two adoptees, but about 25 percent of the more than 160 such sets in my files include one adoptee and one biological child—many seemingly infertile women say that once the adoption process was under way, they relaxed and became pregnant. I have even known couples who adopted a child just before or just after delivering triplets conceived by assisted reproductive methods, generating three pairs of virtual twins in one family. Some virtual twin pairs came into being through even more exotic means, such as adoption plus surrogacy, adoption plus embryo donation, and marriage of same-sex partners whose children had different dads.
Virtual twins are closely matched in age and time of arrival in their family, but they have no genetic connection. These defining features make them an ideal contrast to identical twins raised together and apart. In fact, they are reared-apart identical twins in reverse because virtual twins share their environments but not their genes, whereas reared-apart identical twins share their genes but not their environment. Most adoption researchers study ordinary adoptive siblings who differ in age and time of entry in their new home. They do so largely because they believe that these pairs are more plentiful and easier to find than virtual twins, and perhaps they are, but I am still finding virtual twins. They are excellent subjects for determining the degree to which living together could make people display similar, as well as dissimilar, habits and behaviors, and they outperform ordinary adoptive siblings on these measures because their ages and arrival times match so closely.
Virtual twins are much less alike in general intelligence and in their strengths and weaknesses in specific verbal and spatial skills than are identical and fraternal twins, even those raised apart. The modest intellectual resemblance that virtual twins show in early childhood probably reflects their common rearing, but it fades as they approach adolescence when new genetic effects and unique experiences kick in. One dad told me he expected to see some behavioral differences between his two daughters, Judith, who was adopted, and Sally, who was biological, but the extreme contrasts in the girls’ abilities and personalities astonished him.
Virtual twins come into being one other way, and that is why the Colombian brothers are so important: the switching of Carlos and William that separated the identical twins simultaneously crafted two virtual twin pairs: Jorge and Carlos in Bogotá, and Wilber and William in La Paz. But there is more to this story: when twins are inadvertently switched, an exclusive and exceptional class of virtual twins emerges because its members believe they are fraternal twins, as do their parents and other relatives. After all, their mothers gave birth and took two babies home from the hospital. The math adds up and no one asks questions. The brothers of Bogotá and the brothers of La Paz became unwitting members of this unusual group.
True, these virtual twins and their families were puzzled by the striking physical differences between these siblings. Friends of the Bogotá twins would sometimes ask, “How could you be twins?” or joke that “you’re too handsome to be in your family!” Even more prescient, relatives in La Paz told Ana, “Maybe one of your kids was switched at birth? Ha ha!” She would sometimes say, “My poor little son [William], it seems he has been exchanged.” And when her boys threw fists at each other, as siblings sometimes do, Wilber would yell, “You’re not my brother!” or “You were picked up on the street, and my mom and dad fed you for free!” But everyone knows that fraternal twins can be quite different, so the jokes and threats were neither made in earnest nor taken seriously.
I think of these exclusive virtual twins as the most exceptional of unrelated siblings, whose research status parallels that of reared-apart identical twins, who are the most exceptional among multiples. If these particular virtual twins, who always believed they were fraternal twins, are more alike in taking tests or running races than ordinary virtual twins (who always knew they were unrelated), perhaps belief or investment in being a twin enhances similarity. I would not expect the two types of virtual twin pairs—those who believed they were fraternal twins and those who knew they were not—to differ in how much they resemble one another for traits significantly affected by genes. Parents who think that their identical twins are fraternal still find similarities in their children’s behaviors, so their misbelief about twin type does not affect their perceptions of their children or the children’s outcomes.23 Still, the degree of resemblance across characteristics of the ordinary and extraordinary virtual twins is an empirical question that researchers could and should address. However, the very small number of such extraordinary virtual twin pairs precludes a proper test of this notion—the newly found Colombian twins increased that number from seven to just nine.
* * *
The multiplicity of relationships generated by the Colombian twins continued to expand and included two sets, William and Carlos, and Jorge and Wilber, who have never been studied before because they were unknown to researchers until now. We have no word to describe them, so I chose replicas, because they truly are replicas, not originals. If you think of two people standing together in front of a mirror, the reflection in the glass is a re-creation of the original; it preserves the important elements, but it is still a copy. Replicas are an entirely new kinship, created accidentally and for the first time in Colombia because of the switching of two twins from two identical pairs.
The members of each replicated pair share neither their genes nor their environment. However, each of the four individuals can be paired with an identical copy of his accidental brother:
• Jorge was raised with Carlos, but they share no genes. Because Carlos is genetically identical to Wilber, Jorge and Wilber are replicas.
• William was raised with Wilber, but they share no genes. Because Wilber is genetically identical to Carlos, William and Carlos are replicas.
Replicas make possible a new research design, and a little reasoning reveals the great value of these rare pairs. If, for example, Jorge and Carlos are more alike as accidental brothers than the replicated pairs in choice of clothes, taste in food, or pick of women, this would tell us that a shared environment enhances the similarity of those behaviors. If they are not more alike, this would suggest that a shared environment does not make siblings the same. Both Bogotá brothers had professional goals in mind, but were Jorge’s inspiration and drive more like Carlos’s or Wilber’s? Neither La Paz brother advanced beyond the fifth grade, but would William’s verbal skills more closely match those of Wilber or Carlos?
Keeping Them Straight
Experimental psychological research shows that it’s easier to remember faces than the names that go with the faces. Researchers still debate why this is so, but this truism about memory comforted me when I found it difficult to remember which brothers were the real twins and which ones were raised in Bogotá and La Paz.24 I had trouble keeping the four individuals, accidental brothers, reared-apart twins, and replicas straight until I saw them for myself. A chart with pictures and captions would have helped me greatly at the beginning.
As convoluted as the twins’ different relationships appeared to be to us, they paled in complexity relative to their relationships with their parents and siblings. The Bogotá brothers grew up with a sister, Diana, who is four years their senior. Once the switch was uncovered, she was still Jorge’s biological sister but instantly became Carlos’s unrelated sister, William’s biological reared-apart sister, and Wilber’s replicated sister. The accidental pair in La Paz had four older siblings, whose characteristics yielded even more genetically and environmentally varied and complex comparisons. And we could compare the La Paz parents with the son they raised and the son they did not.
Putting It All Together
Having worked with reared-apart twins before, I had access to the life history booklets, personality questionnaires, and twin relationship surveys we would need. One of my students, Lissette Bohorquez, who is of Colombian descent, and Yesika helped translate into Spanish several forms for the brothers to fill out, and my Barcelona colleague, David Gallardo-Pujol, provided me with some surveys and inventories that were already available in Spanish.
Interpreters, Translators, and Testers
There is a critical distinction between interpreters and translators. Interpreters transform spoken words from one language into another, usually on the spot. Their accuracy depends not only on their expertise in both languages, but also on their familiarity with a particular subject. In contrast, translators typically work at their leisure from written materials and can consult grammatical texts, seek advice from native speakers, or type expressions into Google Translate.25 We were hoping to find a professional interpreter with a background in psychology, and we did.
Alberto Orjuela is a Colombian-born interpreter and translator who was seven in 1960 when he relocated to New York City, where he lived for nineteen years. He earned a bachelor of arts degree in social psychology at New York’s Stony Brook University in 1974 before returning to Bogotá in 1979 “to practice what I love—both translation and interpretation.” He is also punctual to a fault, a trait I value in anyone I hire because I suffer from it myself.
After a series of introductory emails, we “met” Alberto for the first time during a three-way Skype interview in March 2015. Alberto, in his early sixties, has dark hair, a ruddy complexion, and a pleasant smile. He agreed to work six or seven full days with unpredictable hours and accompany us on the arduous journey to La Paz.
Finding an interpreter was just one of several tasks to complete before leaving for Bogotá. Another was to have the twins complete a standard general intelligence (IQ) test, namely, the Wechsler Adult Intelligence Scale-IV, or WAIS-IV. Comparing the college-educated city boys with their identical country-raised counterparts who had not advanced beyond the fifth grade would be a unique addition to reared-apart twin research because I could not recall any other reared-apart twins with this degree of educational difference. One of Yesika’s former instructors, Ligia Gómez, and her associate, Diana Ramos, would do the testing.
Controversies about the relative contributions of nature and nurture to IQ scores are often bitter and contentious and have surrounded IQ findings from reared-apart twin studies for decades. One of the biggest disagreements is whether the similar IQs of reared-apart identical twins reflects their shared genes or similar features of their different home environments and educational backgrounds.26 We knew the Colombian twins would shed some light on this issue.
DNA: Identical, Fraternal, or None of the Above?
We learned that both pairs of twins were identical (monozygotic), based on the DNA findings Yunis discussed on Séptimo Día. We would later gain access to the full report, which shows that Jorge and William, and Carlos and Wilber, match perfectly on twenty-one different DNA factors, a nearly impossible feat for any other two people.
I wanted to extend the genetic analyses to the burgeoning area of epigenetics, a hot spot in the genetics field concerned with how and why some genes are expressed, or “turned on,” and how and why other genes stay silent, or “turned off.” The finding that identical twin similarity is less than 100 percent for major psychiatric disorders, such as schizophrenia (50 percent) and Alzheimer’s disease (60 percent), has led researchers to explore epigenetic events that may explain why one twin is affected and the other is not.27
Epigenetics was originally tied to the unknown processes that enable a fertilized egg to develop into a mature organism, but since the late 1960s it has focused on changes in gene function and expression that vary among our different types of cells and that do not involve changes in DNA. The prefix epi means “above,” so it is reasonable to think about epigenetic processes as acting above, or outside, the full array of a person’s genetic sequence.28 Epigenetic changes do not alter the DNA sequence, so they have been called soft inheritance.
The possibility that the urban versus rural environments and exposures of the reared-apart identical brothers could be linked to differences in their epigenetic profiles was of great interest. Chemical pollutants, more common in cities, may have affected the Bogotá brothers more than the La Paz ones, whereas animal and plant products from the family farm may have uniquely affected the La Paz pair.29 Which genes are expressed, as well as when and why, are topics of great interest to geneticists, with significant implications for members of the general public.30 Researchers conducting epigenetic studies focus on the regions of the genome that are thought to affect the expression of a particular gene.31
Identical twins who differ in a behavior or a disease are ideal for uncovering the epigenetic factors responsible for that difference. Identical twins share their entire genetic sequence, so if one twin is overweight or one twin is diabetic, the difference must be tied to a nongenetic event. Knowing what silences gene expression in one twin or activates it in the other may help researchers find ways to manage or mitigate behavioral and medical problems experienced by members of the general public.
It is likely that identical twins have similar genetic susceptibilities to some conditions and that a nongenetic event triggers the condition in just one twin. In 1987 the health science PBS series Bodywatch featured identical twins Jane and Joan, only one of whom developed diabetes. Diabetes had affected some members of their family, but only Joan developed the condition after contracting an infection that seemed to linger. Studying twins has, in fact, provided support for epigenetic contributions to schizophrenia, bipolar disorder, dental characteristics, and liver disease.32 And researchers have found specific epigenetic changes in female identical twins with breast cancer whose sisters were not affected. This knowledge can help identify warning signs in individuals at risk and offer insight into the origins of this and other medical conditions. Of course, epigenetic differences in identical twins show that, strictly speaking, they are not exact genetic duplicates of one another. That is, despite their identical genes, environmental influences inside and outside the womb can intervene, making identical twins differ in body weight, heart functioning, and perhaps sexual orientation.33
Researchers have also found evidence suggesting that epigenetic changes can be passed down through generations. People exposed prenatally to famine in the Netherlands during the terrible winter of 1944–45 showed less methylation of genes—the addition of a methyl group to DNA that affects how genes are expressed—involved in growth and development than did their unexposed siblings when measured sixty years later. And epigenetic differences between identical male twins, one gay and one straight, may help explain these twins’ sexual orientations.34 The challenge is to separate the effects of epigenetic mechanisms from other possible explanations.
An epigenetic study of reared-apart identical twins, comparing their genes that have been turned on or turned off, had never been reported, so ours would be a first. Adding to the novelty of this analysis would be information from two virtual twin pairs, two replicated pairs, and an older sister paired with the biological and unrelated brothers with whom she had been raised, as well as from a biological brother she had never known. These unique pairings within the same family would allow us to compare the similarities and differences of pairs who shared genes but not environment, environment but not genes, and neither genes nor environment. We would face limits to what we could conclude from just a few pairs, but epigenetic differences between the separated identical twins could suggest that any health differences between them might be tied to their environment, both inside and outside the womb. It was also possible that the separated identical twins would be more alike than the accidental brothers raised together, evidence of genetic influence on genetic expression. We planned to map out the different twin and sibling pairs with regard to epigenetic resemblance.
My friend and colleague Dr. Jeffrey Craig of the School of Medicine at Deakin University, Geelong, Australia, is an epigenetics expert. Originally from the United Kingdom, he has been a trailblazer in using twin studies to address epigenetic questions. One study looked at newborns with reference to how maternal nutrition, assisted reproduction, and alcohol intake can affect how genes are expressed (methylation pattern).35 Identical twins showed more similar gene expression profiles at birth than fraternal twins, although each twin had a unique pattern. For example, the greater resemblance among identical than fraternal twins for the expression of a particular gene suggested genetic influence on which genes are turned on or turned off. However, the profiles of some identical twins were less alike than the profiles of some fraternal twins and even of unrelated pairs, showing that genetic expression is a complex process. In a related study twins with a shared placenta had more discrepant methylation profiles than those with separate placentae.36 The reason for this is unknown, but greater twin-twin competition for resources in the womb may be one explanation.
Jeff provided me with special tubes for collecting cell samples (buccal cells, from inside the cheek) from the four Colombian twins and older sister Diana to be analyzed in his laboratory.
The Rest of the Schedule
We hoped to compare nearly everything about the twins, including their mental abilities, personality traits, and physical skills, not to mention their past endeavors, current concerns, and future dreams.
Woven throughout the twins’ communications was a sense of their growing excitement about a visit from an American psychology professor (me) and social worker (Yesika). We were just as eager to meet them, anticipating that their unique situation might reveal new information about human behavior and family relationships. Research participation would be a new experience for the brothers, and they weren’t quite sure what to expect, but all four had checked out my credentials and seemed impressed. Jorge, ever the leader, emailed messages with warm words of welcome. We had warned them in advance that their days would be filled with interviews, inventories, body measurements, and videotaping, but the stack of materials we set before them would still seem daunting, as it is to most reunited twin participants. But like other reared-apart twins, they were eager to learn more about the factors affecting their abilities, predispositions, likes, and dislikes, and how they measured up against each other. They also knew that by engaging in the various tasks, sharing their life stories, and just being themselves, they were bringing us closer to answers to complex developmental questions. All four young men distinguished themselves as among the most enthusiastic and charming of the study participants with whom I have worked.
The Bogotá brothers had never been to the La Paz brothers’ childhood home, a journey that Jorge was especially eager to make to gain a better appreciation for his twin’s past and present life. In fact, setting aside a full day for travel to La Paz, a trip that took us nearly twelve hours from Bogotá (longer than the usual seven hours because we stopped along the way), was both an essential part of our visit and William’s precondition for participating in the project. He wanted us to experience the home environment in which he and Wilber had been raised.
As the date for our departure for Bogotá drew closer, I sensed the enormity of this story more than I had before, perhaps because the groundwork was done, leaving me time to reflect. Clearly, this mission would electrify my twin studies colleagues, who thrive on gathering and interpreting new data. But the twins’ story also captured the universal themes of family, loyalty, love, disappointment, heartache, and reconciliation that move the hearts and minds of general audiences. Who among us has never questioned our relationship to our family members? And who has never experienced the loss of a loved one?
I wondered constantly how the Colombian twins were handling their discovery and its aftermath. Based on the television interviews and email correspondence, I sensed adaptability and liveliness in the four twins who were trying desperately to right an unimaginable wrong. It was not easy for them, especially for the exchanged brothers, who were questioning their past and future relationships with their parents, siblings, aunts, uncles, and accidental twin. The four brothers were also learning that reality can be a kind of twilight zone—a land of both shadow and substance. And they wanted to learn more about how their minds and bodies compared with one another’s and with the minds and bodies of other reared-apart pairs. Researchers are not the only people who find twins intriguing—the fascination that twins have with themselves and with each other is endless.