Carlos had been repeating falsehoods all his life. He said that he was born in Bogotá on December 22, that his mother’s name was Luz, and that he had an older sister named Diana and a fraternal twin brother named Jorge. He also told people that he had never been to Vélez, a city in Santander. But Carlos was not a liar—he was only telling the truth as he knew it. He had no way of knowing that his real twin brother, Wilber, was living the life both should have had in an isolated farm area with no modern amenities. And Wilber had no way of knowing he was growing up with an unrelated, accidental brother, the sensitive William, who had taken Carlos’s place.
Luz, the mother of Jorge and Carlos, had delivered twins and brought two babies home. But sometime between the arrival of her twins and their discharge from the hospital, one of her twins changed places with another newborn. This twist of fate turned Carlos into Luz’s accidental son, as well as Jorge’s accidental twin and Diana’s accidental little brother. The switch also transformed Carlos into an unintended nephew, grandson, and cousin. He also became an accidental uncle to Jorge’s young son, Santiago (“Santi”). Santi lives with his mother, Jorge’s former girlfriend, and grandmother just down the street from the apartment Jorge and Carlos share, making it easy for father and uncle to see the boy often.
* * *
Jorge and Carlos grew up believing they were twins, but they inhabited separate interior worlds. Why? One of the great psychological insights of the late-twentieth century was that living with someone does not make you alike. My findings on virtual twins—individuals of the same age raised together from birth, but who are unrelated genetically—provide striking examples of how shared environments do not produce shared behaviors. Most of these pairs include two children adopted into the same family within the first year of life, while some pairs include one adopted child and one biological child born just before or just after a couple’s decision to adopt.1 Couples experiencing infertility can either adopt children or try to have biological children by one of several assisted reproductive technologies (ART). But adoption agencies sometimes have two children in need of a home, instantly transforming their clients into larger-than-expected families. Some couples try adoption and ART—and end up with one adoptee and one biological child. Parents without partners who decide to live and raise their kids together, adoption plus embryo donation, and adoption plus surrogacy have created other more exotic virtual twin pairs. Virtual twins generally turn out to be different in general intelligence, specific mental skills, peer networks, and body size, and they become less alike with time.2
When related family members are “chips off the old block”—meaning they are similar in some personality traits or personal habits—these similarities come about because they share genes, not because they share environments. As a young child the actor Skandar Keynes, the great-great-great grandson of Charles Darwin, looked a lot like the famous founder of modern evolutionary theory.3 Different gene combinations that may or may not be passed down intact to future generations influence most physical features, such as jawline and nose shape. This explains why some grandparents and grandchildren vary in how much they look alike and in what ways.
Family resemblances are not limited to physical traits. Identical twins raised apart usually find that they were acting the same way and doing the same things in their parallel universes. The firefighter twins from New Jersey, Mark Newman and Jerry Levey, were fighting flames in different cities and flinging good-natured insults at their friends. Barbara and Daphne, the British reared-apart pair known as the “giggle twins,” found humor in just about anything, laughing uncontrollably when they were together but with no one else. These identical twins showed little interest in politics; drank their coffee cold, black, and without sugar; and had suffered a miscarriage in their first pregnancy before each produced two boys and a girl. They were also the proud co-creators of Twin Sin, a drink made of vodka, blue curaçao, crème de cacao, and cream. Both Samantha Futerman and Anaïs Bordier, identical reared-apart Korean twins, were ignoring their lactose intolerance while they continued to consume cheese in their respective Los Angeles and Paris kitchens. Both twins were also scratching at hives and rashes.4 These twins’ similarities, expressed miles apart, were largely reflections of their common genes. All these twins exemplify “gene-environment interaction,” or the expression of the same genes in different settings.
But, of course, genes aren’t everything because not all the behaviors of these twins matched perfectly. Different environments can also interact with the same genes to produce different outcomes. Samantha was more outgoing than her twin sister, perhaps because she grew up in an ethnically diverse community that included people of Asian descent, whereas Anaïs was raised in a homogeneous Paris suburb where people would mistake her for a maid. Samantha also had two older brothers who adored and protected her, whereas Anaïs was an only child.5
The environments that set us apart from our family members in personality and outlook are those that we do not share with our relatives, such as taking an around-the-world voyage, having an influential professor, or taking up a challenging sport. Jorge and Carlos had many individual academic and athletic experiences that the other did not have because they preferred different things. Like all of us, their genes predisposed them to certain activities and events and away from others.
* * *
Jorge and Carlos were the second and third children of thirty-six-year-old Luz Marina Castro Chavez and forty-six-year-old Norman Enrique Bernal Triviño. Although Luz’s doctor told her to expect identical twins, her sons were clearly not identical. Assuming they were a fraternal pair, Luz and everyone else figured that they had inherited different sets of genes. But the boys’ differences in appearance and behavior had a simpler explanation—they were not genetically related, a truth that went undiscovered for twenty-five years. Meanwhile, Jorge and Carlos withstood the stares, jokes, and comments that inevitably surfaced when they told people that they were twins.
Jorge’s and Carlos’s interests diverged most dramatically during childhood. Carlos was the more serious and focused student, a mind-set that is still evident today as he pursues his professional career in accounting and finance. Bogotá’s educational and cultural opportunities gave expression to Carlos’s natural drive and inclinations to achieve in his chosen field. As such his unintended city proved to be a good match, allowing him to pursue his interests and talents at school and at work. In this respect he is quite different from Wilber, his identical twin, who has never been interested in continuing his education. It is impossible to know whether Wilber would have been more interested in education if he had been the twin who grew up in Bogotá—he has the same mathematical interests as his reared-apart twin, but never had the chance to explore his abilities to the fullest. It is also impossible to know whether Carlos, like his real brother, would have written off education had he grown up in the country, but it is certainly possible.
Different rearing environments seem to have had some varying influences on the true twins Jorge and William. Drive and desire are Jorge’s hallmarks. In Bogotá he was pursuing a career in engineering while working part time in his field developing methods for gas and water transportation. Admittedly, he is often sidetracked by his love of football, which takes him to competitions across the country and around the world. However, events beyond his control, such as Colombia’s plummeting oil prices, have also delayed his progress because he was laid off from his job.
William, his identical counterpart raised in La Paz, can also count drive and desire among his finer attributes, but the limited opportunities and financial constraints of his family meant he could not pursue his education, no matter how determined he was. He eventually was able to express these tendencies, which are partly genetically based, when he moved to Bogotá, and especially after he met his twin and received the assistance and support he clearly craved and required.
* * *
Reaching his goal of earning specialized credits and owning his own financial consulting business is within Carlos’s reach. He is closer to fulfilling his goals than Jorge is to becoming an engineer. Jorge, always a serious, but more casual, laid-back pupil, is progressing more slowly, not yet certain of the specific path he wants to pursue. He has not thought this through, partly because he follows his favorite football team, Atlético Nacional, wherever it plays, even traveling to Japan to watch the team compete for the 2016 World Cup. He cannot afford to do this, but he borrows money from close friends who trust him to pay them back. Jorge’s love affair with football began in the seventh grade when a classmate introduced him to the game. His near obsession with this sport irks his brothers, but passion is a trait he shares with William, who has become a consummate weight trainer. The same genes inhabit the cells of these twins, but their different environments guided their expression.
In high school Jorge preferred rock to Carlos’s taste for hip-hop and rap. Their clothing styles were also different. Jorge dressed in jeans and T-shirts, while Carlos wore the baggy pants and oversized tops of the hip-hop set—and both styles infuriated their mother, Luz. Their sister, Diana, recalls that Carlos looked funny in big clothes but “came to his senses” when he started studying accounting—then he chose more fashionable and traditional attire, paying particular attention to his hair, paralleling his twin’s attention to fashion in La Paz. Jorge also thought about his hair, but he let it grow to his waist and pulled it together in a long ponytail, another point of contention with his mother. But to the relief of Luz and her sisters, neither Jorge nor Carlos used drugs or associated with classmates who used them. “They both have excellent values,” observed their elegant aunt Leonor.
Growing up in Bogotá, with its many educational and recreational opportunities and events, allowed Jorge and Carlos to be themselves, doing what came naturally. “They were not typical twins,” observed another of their five aunts, Maria Teresa. Hers was an astute—prescient, really—observation, because Jorge and Carlos weren’t twins at all.
* * *
By the time Luz was pregnant with her twins, she had lost her job as a seamstress, so she couldn’t afford an ultrasound, an important procedure for managing high-risk pregnancies. Once the twins were born, to make ends meet Luz cleaned houses, washed clothes, and ran errands to give her children the best future that she could. Their father, Norman, was variously employed in wood, carpentry, and machinery businesses; worked for a while in a restaurant; and drove a private car—“he was a man of all trades,” according to Jorge. But Norman was rarely around and showed little interest in, or affection toward, the children he had had with Luz. Regardless, Jorge and Carlos were loved and well cared for. They were raised in an all-female household, where everyone doted on them. Their pretty sister, Diana Carolina, older by four years, adored them, jumping up and down when they finally arrived at the family’s two-story home. They were also cherished by their grandmother, Leonor Chavez, and the two aunts, Maria Teresa and Blanca Cecilia, who lived with them; Blanca Cecilia considers herself their second mother. Maria Teresa’s daughter, Gloria Andrea, lived with them as well—Gloria was the same age as Diana, but she played mostly with Carlos.
* * *
Luz had three other sisters—Leonor, Ana Rosa, and Maria Esther (Blanca Cecilia’s fraternal twin)—who lived in Bogotá and were always around for the children’s birthdays, communions, and graduations. Leonor, always bedecked in jewelry and wrapped in a stylish suit, acknowledged that Luz had had a difficult life and had worked hard to support three children on her own. Luz had insisted that they receive a good education so they could advance socioeconomically—she could read and write, but had gone only as far as the eighth grade. Luz’s sister Ana Rosa had paid for her niece and nephews’ high school education, but the assistance was never really enough. Jorge estimated that his mother’s yearly earnings amounted to US$2,520, much less than what she had previously earned as a seamstress.
The family of eight lived in a modest five-bedroom house in a lower-middle-class area of Barrio Quiroga, far from the center of the city—housing costs and neighborhood quality generally dip as travel time to the heart of Bogotá increases. The house, now occupied by their aunt Maria Teresa and cousin Gloria, looks badly out of place on their quiet street—it is essentially a brown brick box dwarfed by two much larger structures on either side. A brick wall inlaid with white metalwork surrounds the entrance, but provides little security because even a child could easily hop over it. The house has a living room, kitchen, hallway, and bathroom on the ground floor. Stairs lead to the second floor, where Jorge, Carlos, and Diana had shared a large room for sleeping; other family members used other small spaces on that floor for bedrooms. The house sounds large but was cramped for four adults and four lively children, although it is similar in quality to most other homes in their working-class neighborhood. Jorge and Carlos lived there for the first nineteen years of their lives.
Their childhood home had a television, tape recorder, musical instruments, and a refrigerator. They played with store-bought toys and rode their bikes around the neighborhood. But the family was not wealthy—Jorge would have liked to have had a better bike, Carlos wished the family could have had a washing machine, and both would have enjoyed working with a computer. Their La Paz counterparts, William and Wilber, didn’t have a refrigerator or a washing machine, but it never occurred to them to wish for these things. Both William and Wilber had wanted bicycles, but finding a place to ride them would have been difficult, if not impossible, because there were no roads nearby. Both brothers would also have liked to have had a TV, but virtually no one in their area had one because they also didn’t have electricity. Indeed, neither brother listed electricity as something he would have wanted in their childhood home, perhaps because none of their friends had it.
Catholicism was important to Luz and she attended services frequently. “She always forced us to go to church,” Jorge said. Neither brother was seriously religious when they were growing up, although both have turned toward religion in their own way since learning about their twins, probably because learning of the switch has made them think more deeply about who they are and why. Aside from Luz’s insistence that her children attend church, she was a fairly lax disciplinarian. The children always exploded in laughter when she charged at them with a soft slipper. Luz scolded her sons on occasion but never really punished them, in the belief that reasoning with children has a greater influence on their behavior.
Although Jorge and Carlos were rather different children—Jorge was people-oriented and playful; Carlos was self-reliant and serious—they sometimes played together, usually in groups with other children. This is typical, because many fraternal twins and siblings are less inclined than identical twins to do things together in the absence of other children. (As a young fraternal twin I sometimes complained to my mother that I had “no one to play with,” even when my sister was sitting in the next room.) Young Jorge and Carlos and their friends once had great fun walking along the main street of their neighborhood and throwing paper inside buses that had stopped. The kids did this for three days. When Luz learned what they were up to, she wanted to ground her sons but relented—too soon, apparently, because they continued to do this until one day a bus driver started to chase them. The children ran seven blocks to a park and hid, but then the driver, “this big guy,” got out of the bus and came after them. When the driver tripped and hurt his arm, Carlos stopped running and the guy grabbed him, put him on the bus, and drove him home.
Luz was furious, scolded Carlos, and threatened to spank Jorge when he came home. But in the middle of her anger, Luz tripped and fell, and they all just laughed. Jorge admitted to his mother that when the driver lost his balance, he ran back and hid in a store. “Why did you run back?” Luz asked him. “You should have run forward so you wouldn’t get caught.” Her words seem surprising for a religious, conscientious mother who was determined to raise her children the right way—she was not into punishment, but she was into protection. Many incidents like these triggered the slipper attacks, but the children only pretended to cry, and when Luz left the room they would start laughing. This would bring her back and the fake crying would begin again.
Luz died of stomach cancer when she was fifty-seven, a terrible blow to her sons, her daughter, and her sisters. Jorge and Carlos never told their father that their mother had died because Norman’s own health was poor, and they thought that the news might make him worse. In fact, Norman died of a heart attack about a year after Luz died. Carlos barely acknowledges the father who took so little interest in his family. He and Norman fought bitterly during the few times Norman did show up to visit; they mostly argued over Norman’s failure to bring Luz some money. Unlike Jorge, who accepts people and situations as they are and who generally does what seems appropriate and expected, Carlos did not attend his father’s funeral. He cannot always contain his extreme resentment of his father and uses angry expressions and impatient gestures when he speaks about him. Carlos believes that Norman had no influence on his life, but that remains to be seen—when Carlos becomes a parent, he may try especially hard to give his own children the fatherly love and attention he was denied. In contrast, his love for his mother was so great that it’s hard for him to talk about her. If not for the love lavished on them by their aunts, Luz’s children, then in their twenties, would have found losing her unbearable.
Some family members say that Jorge looks like Norman, which makes sense because he is Norman’s biological son, but they say that Carlos also looks like Norman. I find this fascinating because, in nearly all the switched-twin cases I have known, mothers have commented on the resemblance of the switched child to relatives on the paternal side of the family. A father’s own perceptions that a particular child looks nothing like him does not mean that the child is not his or that he will not care for the youngster. But fathers tend to invest more time and effort in children who look like them and whose mothers they see as trustworthy and faithful.6 Of course, Carlos’s family members did not offer these comments with questions of his paternity in mind—and, more important, they had no way of knowing that Carlos, the different-looking child, had no biological connection to Norman or to Luz. Perhaps Norman’s failure to see any resemblance between himself and Carlos made their relationship especially contentious. Carlos too was hot tempered, which was different from Norman and Jorge, both of whom tended to remain calm. In reality Carlos shared his temperament with an identical twin he didn’t know he had.
School Days
All three of Luz’s children attended district schools, which are public and not as good as the costly private schools, but Luz saw to it that they went to the best ones in the area. She enrolled Jorge and Carlos in the school for boys and Diana in the school for girls. Kindergarten was an all-day affair, lasting from 7:00 a.m. to 4:00 p.m. Then, from the first grade through high school, the day began at 6:30 a.m. and ended at noon. The boys’ high school was the relatively selective Colegio Restrepo Millan, housed in an imposing redbrick structure that has a large open area for assembly and recreation, a world away from the uninspiring field where the La Paz children played. The Colegio’s current mission is to promote leadership in social and cultural projects, based on research and teaching in science and technology.7 Gaining admission to Colegio Restrepo Millan was difficult, and the boys’ older cousins had been forced to leave because they couldn’t keep up. Some people doubted that Jorge and Carlos would succeed at such a school, but Luz disagreed. “You guys are the only ones who decide that,” she told them. Both Carlos and Jorge graduated from the school, enrolled in college, and earned certificates in specialized topics, Carlos in finance and Jorge in mechanical engineering. They worked during the day and attended school at night, and were still doing this when we met them. Diana completed college with a major in social management, followed by one year of postgraduate study. She works as a public information officer for Colombia’s national archives, advising people how to protect and preserve films and photographs. Diana is also her brothers’ confidante and advice giver, a role that comes easily to her, especially since their mother’s death.
Colombia is a country where people do not read for pleasure, but Diana is an avid reader. Neither Jorge nor Carlos reads much—Carlos follows city news on the Internet, but the last time Diana saw him with a book was two years ago. In fact, Diana does not recall having many books or newspapers around their childhood home, although a Spanish-English dictionary and world atlas were available. Once she started working and earning a salary, she ordered and paid for a newspaper subscription. “Maybe my profession draws people into reading,” she suggested. I believe that the reverse is true, that people who enjoy reading and acquiring information are attracted to a job involving access to historical records and audiovisual materials of national significance.
Moving On
When Jorge and Carlos were nineteen, family squabbles prompted them, Diana, and their aunt Blanca Cecilia to move to a three-bedroom apartment in historic Candelaria. Candelaria is the charming colonial district of Bogotá known for its baroque and gothic churches, art museums, quaint hotels, educational institutions, and trendy restaurants. Candelaria draws hundreds of tourists year-round but especially during Holy Week, when a huge procession moves from Monserrate, the sacred mountain and iconic church that loom over Bogotá, to the streets below. But Candelaria is not just for tourists—Jorge and Carlos’s family lived in one of the more residential, less upscale areas. Luz died two years later, in 2009. Deeply troubled by memories of their mother and sister, the foursome left Candelaria for a two-bedroom apartment in the somewhat nicer La Isabela neighborhood of Bogotá. They were joined for a while by Diana’s boyfriend, Andres, but Diana and Andres eventually left, taking Blanca Cecilia with them. During this time Jorge lived intermittently with his girlfriend and her mother.
Soon it was clear that Jorge was not ready for marriage. But when he became a father, he and Carlos moved to an apartment in the working-class neighborhood of Barrio Bachué, just a block from Jorge’s son, Santi. Jorge and Carlos still live there, along with their aunt Blanca Cecilia, in a duplex apartment that has two bedrooms, two bathrooms, a kitchen, and a living room. The furnishings are tasteful but a bit sparse. A table in the living room holds some amateur sports trophies that Jorge and Carlos won over the years, Jorge exclusively in football and Carlos mostly in basketball but also football. Among their proudest moments are Jorge’s college championship in football, when he was eighteen and played for the team fielded by the SENA (Servicio Nacional de Aprendizaje, or National Learning Service); Carlos’s district championship in basketball, when he was nineteen and played for the Kanguros (Kangaroos); and their childhood championship in football, when the twelve-year-olds played for Jaqu Mate (Checkmate) with other boys in their neighborhood.8 Most striking to visitors is a photo of a smiling Santi with his arms around Jorge, whose long dark hair contrasts so sharply with his now closely cropped cut. He is wearing an old yellow Colombian football jersey with the word AGUILA (Eagle) emblazoned across the front over the words MI GUERRERO DE SANGRE (My Blood Warrior).
The brothers’ apartment is on the second or third story of a big complex, reachable only by an outside stairway. A flat piece of ground separates it from an identical apartment building and provides a convenient play area for young children. It is a comfortable place to live, but hardly the somewhat upscale residence implied by the media once reporters learned of the twins’ story. Nonetheless, Carlos and Jorge had choices that William and Wilber did not have or even know about.
Accidental Brothers of Bogotá
One brother in each accidental pair was born and raised where he belonged, and Jorge is one of them. He is the natural leader, the one who answers emails, does interviews about the twins’ switch and reunion, and serves as general spokesman for the gang of four. To promote solidarity among his new band of brothers, he rules with a firm but tender touch. Jorge was the only one of the four twins who answered my initial inquiry, responding: “Hola, Con mucho gusto eres bienvenida a Colombia y compartir todos una nueva experiencia.” (Hello, you are welcome in Colombia to share a new experience.) Jorge has a big personality and a big presence, captivating people with his charm, grace, and interest in who they are. He comes alive in the limelight, a role he enjoys but one that his more reserved accidental twin brother, Carlos, finds irritating. However, Jorge is firm in his belief that decisions affecting all four be made together.
Jorge is not big physically. He is slim and just under five feet, seven inches tall. His short dark wavy hair grows neatly and naturally away from his forehead, framing his dark brown eyes and slightly uneven nose. A recent picture shows Jorge and his identical twin brother, William, seated together at a wedding, heads cocked toward one another and touching slightly. It is impossible to tell them apart, especially because of their ears—ear shape and structure are, in fact, genetically influenced features.9 In the photo Jorge is wearing a fancy dark suit and a purple tie—or is he the one sporting the black-and-white checkered tie?
This wedding scene hides how Jorge and William prefer to dress—both are oblivious to Bogotá’s fashion trends, favoring loose T-shirts, jeans, and sweatshirts even as adults. (Even William’s efforts to show off his new physique have not given him a style that matches that of Carlos and Wilber.) Jorge is clean-shaven except for a small goatee sprouting around his chin and accented by a small patch of hair just under his lower lip. When he smiles, he displays two rows of amazingly even white teeth. His boyish good looks have dazzled hundreds of young women who covered his Facebook page with love letters and friend requests once the twins’ story became widely known.
Unalike and Unfamiliar
Some people are hawks (morning people) and some are owls (night people). Which one you are is not entirely a matter of how you were brought up; it’s also a matter of your genes.10 Of course, people can change depending on their assigned work schedules, but adjusting is harder and more unpleasant for some people than others. Jorge is not a morning person—he often breezes into appointments several hours after the agreed-upon time, conveniently blaming some football event or childcare issue for the delay. This tendency can be grating, especially for Carlos, who has deep respect for obligations. But like his reared-apart twin brother, William, Jorge’s manner of smoothing tensions over with such complete sincerity means people never are angry for long. His friends allow him this slack because they see so much good in him.
Alongside his devotion to his favorite football team, Jorge has big goals and dreams, just like William, but Jorge’s desires and plans to achieve them are not fully formed. He worked days at the Strycon Engineering company, designing gas and water lines until the company laid off employees in February 2016. He still takes night classes at the Fundación Universitaria Los Libertadores, where he is working toward a degree in mechanical engineering and is just starting his own construction company. As the only parent in the group, Jorge is closely involved in the care of Santi, who is now five. He gets Santi ready for kindergarten each day, plays with him on weekends, and “loves the kid to pieces.” Jorge’s strong devotion to his son surprised Diana. “I always knew he would be responsible, but I never thought he would be such a good parent,” she told me. However, Diana doesn’t approve of Jorge’s travels to football matches—often sudden or unplanned—because it means leaving his small son behind, but “Santi brings Jorge back to earth.”
Jorge’s passion for football worries the people who know him, because he is a fanatico about Atlético Nacional. There are tense rivalries among fans with different team loyalties, and Jorge has been physically attacked at times just for wearing the wrong T-shirt—he claims he never starts these altercations. When I saw him last, he had an angry gash across his forehead, the result, he told me, of being knocked down by a strong wave at a Brazilian beach. But Carlos thinks a fan of a rival soccer team delivered a blow. They fail to see eye to eye on most things, from valuing privacy to respecting punctuality to washing the dishes. But like their La Paz counterparts, the two have often lived together, as many brothers and sisters do as they transition to adulthood, because as familiar figures in each other’s lives, they can be themselves.
In fact, a growing trend in the United States is for young adult siblings to live together, despite the battles they may have fought as children. Benefits include safety (the presence of a companion), security (emotional support), and solvency (financial relief). The arrangement eliminates the gambling and guesswork involved in living with a friend or someone who answered an ad, because siblings know what they are getting into.11
At least one source of their brotherly tension was eliminated in the last year. Their aunt Blanca Cecilia now lives with them, cooking their meals, cleaning their house, and washing the dishes.
* * *
The accidental switching of Carlos and William turned each into an unwelcome reminder of their accidental lives once they met. Carlos was the baby who suffered from digestion and elimination problems and endured the six-hour bus ride from Vélez, where he and Wilber had been born, to the hospital in Bogotá for treatment.12 He was in the Bogotá hospital’s nursery when Jorge and William were there, and that was when the switch occurred. The baby named Carlos became William when he was sent home to the country, where farm labor was prized and education was not. And the baby named William became Carlos when he was sent home with Luz in Bogotá. Neither twin was responsible for what happened, but as adults William’s initial resentment of Carlos for having the life that should have been William’s was palpable and understandable. And Carlos saw William as embodying the life he should have led, and he found this difficult to accept. It would be a while before these two resolved their feelings.
Carlos’s early life history had some significant consequences. He doesn’t look like anyone in the family he grew up in. His looks clash sharply with those of Jorge, his accidental twin brother, no doubt explaining why friends and relatives sometimes teased both of them about not being real twins. He seems to tower over Jorge, but he is less than two inches taller—no doubt his solid build makes him appear larger than he is. Carlos’s dark hair, which is straight and short, shows the start of an entrada, or receding hairline.13 Male pattern baldness comes from the mother by way of a recessive gene on one of her two X chromosomes. Wilber also shows this trait.
Such X-linked traits seem to skip generations because they are not expressed in mothers whose other X chromosome generally has the dominant gene that does not code for baldness. However, X-linked traits are always expressed in sons because they have only a single X chromosome—their Y chromosome is much smaller and does not carry the same genes as the X. These sons can then transmit the gene to their daughters, who do not express it, but can transmit it to their own sons. That Carlos, but not Jorge, showed the beginning of baldness would not have caused anyone to suspect that Carlos had a different mother because women transmit just one of their two X chromosomes to their sons. In this case Carlos’s X chromosome came from his biological mother, Ana Delina, and that chromosome carried the baldness gene. Jorge also received an X chromosome from his biological mother, but it was from Luz and did not carry the baldness gene. This difference in hair growth would not have seemed unusual to anyone because everyone knows that fraternal twins do not have identical genes. Male fraternal twins and siblings each have a 50 percent chance of inheriting the same baldness gene from their mother. This means that in some twin and sibling pairs, both members will be bald, neither will be bald, or only one will be bald.14
Carlos’s athletic build is enhanced by the stylish tapered shirts and the artfully ripped designer jeans he favors. He wears well-tailored suits to work, showing them off with plenty of dash and a touch of swagger. His nails are manicured and his eyebrows are waxed, part of the fastidious grooming regimen followed by many urban men. Wilber also indulges in manicures and eyebrow treatments, habits he acquired apart from his twin.
Born in the country but raised in the city, Carlos blossomed in Bogotá’s cultural milieu. He easily acquired the urban sophistication, social skills, and self-confidence that allowed him to successfully navigate big-city life—work, school, dancing, music, sports, and women. Carlos worked as an accounts analyst while studying to be a certified public accountant, a credential he earned in May 2015. He is now a financial coordinator for the national education ministry and earned a certificate in tax sciences in February 2017. He prides himself on his individuality and independence, and he is careful about whom he trusts.
Like Wilber, Carlos prefers privacy to publicity and has been reluctant to do anything that brings public attention, but the other brothers’ love of the limelight usually prevails, even though it bothers Carlos. Until recently Carlos had never visited his identical twin in the butcher shop where Wilber works, but when I returned to Bogotá in 2016, sixteen months after visiting in 2015, that was starting to change—lots of things were. Carlos was starting to accept his biological family and place of birth. He was also setting aside his tensions with William, even planning a Mexican vacation for just the two of them. Carlos’s maturity and mind-set were showing through, and the change was impressive. Meanwhile, ever since they had met, Jorge often visited the butcher shop that William managed, working alongside his newfound identical twin, and the two had taken several trips together.
Carlos hides many of his emotions. He wouldn’t talk about his breakup with a steady girlfriend but looks weepy when the topic comes up. He has deep feelings for Jorge, but he expresses them only when he’s drunk. “I love you, brother,” he has been known to mumble, replaying Wilber’s emotional outburst to William as they marched through the jungle. Reserve and reflection can make Carlos appear callous at times. He barely acknowledges the father who abandoned his family, and early on he maintained long silences when anyone raised the topic of growing up in the wrong family. When he did speak he referred to “the grandmother” who had brought him to Bogotá and “the aunt” who had left him there. He had to confront the fact that he really belonged in rural La Paz with a different mother, father, and twin, an existence far removed from the city life he thrives on. Chance kept him in Bogotá—had his Aunt Edelmira brought the right baby back to La Paz, Carlos would never have known the big-city ways that define him.
During my first visit to Colombia, Carlos opened up just once about the shock of learning of the switch, but when I saw him again more than a year later, I got the complete story. What most people took for coldness was a young man trying desperately to come to terms with a life-changing event that caused him to question who he was and how he got that way. Carlos may be William’s unsettling shadow because Carlos enjoys the benefits of city life that William should have had. But Wilber is Carlos’s alter ego—his identical reared-apart twin who is a version of who Carlos could have been.
Carlos has an uncanny ability to look back at himself with humor, revealing details that place him in silly or awkward positions. This behavior seems uncharacteristic of his generally detached demeanor, but is engaging when it appears. Several events from his past make him laugh, although they were awkward and uncomfortable at the time. Once he was sipping a Coke through a straw, picked up the bottle for some reason, tilted it, and ended up spilling the drink all over himself. As a teenager out on a date, his stomach revolted following consumption of a Cuban sandwich—a stack of ham, roasted pork, Swiss cheese, pickles, mustard, and sometimes salami and garlic sauce on bread. “I said “Bye’ fast and started walking back to my house. I was in a cold sweat.” Carlos has had second thoughts about consuming another Cuban ever since. His seriousness is balanced by this lighter comical streak and his willingness to laugh at himself publicly. Both stories seem funny to him now, and while they are entertaining, they are also somewhat self-deprecating. Carlos has admitted to losses of confidence at times.
Carlos does not have the spontaneous, adventuresome spirit that is central to the nature of Jorge and William. Visiting new places is not a high priority for Carlos, but it is for Jorge, who believes that travel opens one’s mind and increases one’s energy—he has no trouble taking credit for encouraging and helping Carlos buy plane tickets so he could finally see the sea. This is not surprising because scores of twin studies show genetic influences on openness to experience (curiosity and open-mindedness) and absorption (emotional responsiveness to sights and sounds). Genes account for about half of the differences among people in these two personality traits. Genetic effects are also responsible for about half the differences among individuals’ social attitudes, such as tough-mindedness and conservatism, and vocational interests, such as adventurous and enterprising professions.15 And genes explain between 72 and 85 percent of the differences in exercise behavior among older adolescent males.16 Thus, the differences between these accidental brothers make sense because Carlos and Jorge have no common genes—whereas Jorge and William share them all—and agree that they disagree in many ways.
CARLOS: Jorge believes he’s always right, and he likes people to follow him. I don’t like to follow anybody. I try to get people to respect what I think.
JORGE: Although he follows me …
CARLOS: I don’t follow you. Jorge knows I support him in many things, but he knows there are many things I don’t like about him. That’s normal.
JORGE: Yes, totally.
Carlos often seems to be on the periphery of events in which he is taking part. At such times he can be analytical, coming up with insights and observations that are important and meaningful. “When my identical twin, Wilber, teases Jorge, Jorge will take it only to a certain point. But Jorge and I, we can take the teasing longer because we’ve known each other our whole lives. Similarly, William should not assume he can tease me to the same degree.” Siblings’ shared social history can be a powerful influence, as it was, and is, in Carlos and Jorge’s case. They tease and annoy each other on a daily basis, pushing each other to dangerous limits, but know they can rely on each other in times of crisis.
Carlos’s reflective mind comes across in other ways. He showed the most interest and curiosity about what we would learn about him and his brothers, not just the physical traits that are obvious, but about their behaviors. Why, for example, was Carlos so terrified when a friend threw an insect at him, causing him to tear off all his clothes? And when they were children and a mouse disrupted their play, Carlos refused to kill the mouse because he was afraid of it. Where does fear of small nonhuman creatures come from?
CARLOS: I said to Jorge, “You kill the mouse.”
JORGE: No, you said, “You kill it because you’re the man of the family.”
CARLOS: I was scared and I just said, “You kill it, you kill it.”
JORGE: I know he remembers because we have talked about this many times.
CARLOS: That’s the point I want to make. He always has to be right.
JORGE: I’m 80 percent sure of what happened.
CARLOS: OK, I’ll just say yes.
Fears and phobias among males are partly affected by genes, on the order of 37 percent for animal fears, such as fear of snakes, bugs, spiders, and mice, although experiences are more influential. Other fears, such as agoraphobia (fear of being trapped, helpless, or embarrassed in public places) and blood/injury phobia (fear of seeing blood or needles), are partly influenced by genes. These fears are largely irrational—Carlos had never had a previous encounter with a house mouse, yet his fear of this small mammal was real. He shared this fright with someone he had never met—his identical twin brother, Wilber, who had nearly killed another soldier who had chased him with a snake. It’s strange to think that two strong, solidly built young men should be so afraid of things that might not bother others, but they are not alone. Reared-apart identical male triplets, Bob, Eddy, and Dave, met by chance when they were nineteen. Eddy had left a small college in upstate New York, but when Bob enrolled at the same school for the next semester, students wanted to know why “Eddy” had returned. This case of confusion brought the two of them together, but they became a threesome after one of Dave’s best friends saw a picture of Eddy and Bob in a newspaper. All three of these muscular, athletically built young men are terrified of needles, a fear we learned about when they visited our allergy-testing lab in Minnesota.17
In modern times wariness of mice, snakes, and sharp objects may seem groundless, but they posed serious threats to life in early human history. Our ancestors who feared them and took precautions survived and passed their genes on to subsequent generations, whereas those who were less concerned died off. Cultural changes occur more quickly than genetic ones.
At the end of their brotherly battle, Carlos seemed to give in to Jorge’s version of the mouse incident, but I believe something else happened. Carlos was accepting Jorge for who he is while realizing that arguing about a mouse is a useless pursuit, a recognition typical of a thoughtful, reasoning person. Carlos also thought a lot about what it would have been like to grow up with his identical twin and decided that having an unrelated brother was more to his liking. Appreciation for individuality and diversity convinced him that being raised with Wilber, who is so much like him, would have been boring. It might also have robbed him of his unique identity. This perspective is understandable, but not tenable, because many reared-apart twins had similar concerns until they met, only to learn that they were not the photocopies they had feared. Investigators are also sensitive to twins’ physical and behavioral variations—a fuller frame, a more even set of teeth, a more serious demeanor. (Only once did I confuse a sixty-two-year-old identical male triplet for another while waiting for one of the three to complete a medical appointment.) Most twins I have worked with found themselves celebrating their similarities and their differences, adding another unique layer to their sense of self—us—something only reunited twins can do. At the same time many what-if questions crowded their consciousness: What if their adoptive parents had been willing to take two children? What if the twin’s adoptive parents had chosen the other child instead? Or, in some cases, why did the biological mother keep one twin and not the other? How did she choose? The twins’ lives could have been dramatically different if their mother had made a different decision or had faced different circumstances.
The Minnesota researchers found it gratifying to see the twins’ relationships evolving so effortlessly, especially among the identical pairs. We chuckled but also loved seeing some adult twins revert to being the twin children they never were, trying to trick us by switching places. Jorge and William, and Carlos and Wilber never knew the fun of fooling their friends by pretending to be the other brother—but, ironically, all four were accidental players in a somber and stressful game of switch.
Reflections
No other case of doubly exchanged adult identical twins has ever been recorded in the history of twin studies. From the first moment, I absolutely believed that the Colombian twins were at the center of the most extraordinary nature-nurture saga ever told. But would the four young men agree to undergo intelligence testing, provide saliva samples for DNA analysis, and reveal their thoughts and fears to two complete strangers? Would they be willing to do this during Colombia’s Holy Week, which begins on Palm Sunday and ends eight days later? Holy Week—the time when Jesus entered Jerusalem and was received with palm leaves—is the most important celebration of the year for Colombia’s predominantly Catholic population; they mark it with nationwide processions and ceremonies.18 Most schools and businesses close, and many people leave town for vacations. I wondered whether the twins would forfeit their free time in exchange for what they might see as an unusual and risky venture. On the other hand, twins are generally fascinated with being twins and are eager to learn as much as possible about themselves.
Most twins also understand the critical role they play in scientific research and enjoy contributing to new findings. Sir Francis Galton of England, credited with founding the twin method in 1875, was actually approached by twins who volunteered to take part in his research. This is unusual because most behavioral science investigators have to work hard to attract a large enough number of participants to produce statistically valid studies. But, like Galton, I find that twins offer their time unsolicited and make efforts to take part in ongoing studies. In response to a twin-family questionnaire I sent by email, one identical female twin replied, “I would love to answer any other questions. Thanks so much.” And after the airing of a television program discussing my work on reared-apart Chinese twins, a mother wrote, “My daughter, who is adopted from China, has a twin sister who was adopted at the same time to a different family. I just saw the show and many aspects resonated. Are you still doing twin research?”19
The greater resemblance of genetically identical than fraternal twins tells us that our genetic backgrounds influence particular behavioral, physical, or medical traits. It works that way with virtually every human characteristic, from verbal fluency to running speed to cholesterol level. It’s a gorgeous natural experiment.