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.
Chapter 7
Discoveries
Twins’ Physical and Behavioral Traits
Getting Physical
Mia and Alexandra, fourteen-year-old identical twins born in China, but raised separately in the lively capital city of Sacramento, California, and the quiet fjord village of Fresvik, Norway, are one-and-a-half inches apart in height and fifteen pounds apart in weight. They exceed the average differences of 0.58 inches and 11.60 pounds for identical female twins reared apart, as well as the average differences of .62 inches and 11.53 pounds, for identical female twins reared together.1 Perhaps Alexandra’s greater exposure to fresh air, natural food, and daily exercise in Norway combined to produce her taller, more robust build, whereas Mia’s need to keep her weight down as coxswain for her rowing team in Sacramento may explain her slimmer figure. However, possible differences in the twins’ intrauterine environment cannot be dismissed. Kelli and Missi, identical twins raised together outside Chicago, differed by four inches at age eight and seven inches by age eighteen. Kelli’s shorter stature resulted from a marginally a
ttached placenta that delivered less prenatal nutrition to her than to her twin sister; Kelli also suffered from cardiac problems. These twins have the same blonde hair, blue eyes, and facial features, but one twin is a smaller version of the other.
Identical twins are more alike than any other pair of people, but they do not show perfect similarity. Identical twins result when a single fertilized egg divides, but a host of prenatal events can interfere with the identical expression of their identical genes. Unequal blood supply in the womb can occur when fetuses’ blood vessels become connected, affecting the two-thirds of identical twins who share a placenta. Known as twin-to-twin transfusion syndrome (TTTS), this condition can create differences in twins’ size and health. It is likely that the twins born in La Paz were seriously affected with TTTS because one La Paz newborn was sent immediately to the Bogotá hospital for treatment. When it comes to birth order, naturally delivered second-born twins are at higher risk for respiratory distress and infection than firstborns. Second-born twins are also at higher risk for newborn death. Not all second-born twins experience difficult births, but their average risk is higher, partly linked to the decreased size of the uterus after delivery of the first twin.2
All four Colombian twins were delivered by caesarean section so they avoided the hazards posed by vaginal deliveries. But the twins give us a glimpse of how life in a modern city and in a remote community can yield close copies but not exact duplicates.
DNA Revealed: Not Another Clone!
In August 2005 Susan and her husband, Steve Kay, had traveled to China with thirteen other couples, including Karen and Tom Lewis, to adopt one of the many thousands of abandoned little girls. China’s one-child policy, instituted in 1979 to curb population growth, restricted urban couples to one child and rural couples to two. That policy, and China’s preference for sons, explains the forced sterilizations of some women and abortions of female fetuses, as well as the widespread abandonment of baby girls. Among the abandoned babies were twins, some of whom were lucky enough to stay together, but others were separated. I am tracking the behavioral and physical development of such twins—they now include Mia and Alexandra and twenty-one other pairs—in the only ongoing study of young separated twins conducted in real time as the children grow up.
Accidental Brothers Page 18