New mothers can also recognize their infants by sound, evidenced by the finding that after forty-eight hours of shared time all new and experienced mothers know their baby’s distinctive cries. And when it comes to touch, most mothers who spend at least one hour with their newborn can pick out their own baby from others just by stroking the child’s skin, which tells us that the texture, temperature, and familiarity of the infant’s skin are the main cues.17
These observations are especially significant in the cases of the Colombian brothers. Neither mother had spent much time with her twins following delivery, so both were unfamiliar with their babies’ smell, appearance, sound, and feel. Ana, recovering from a hernia, never set eyes on Carlos, had little contact with Wilber, and didn’t see William until he came to La Paz when he was one week old. Luz had limited hospital time with Jorge and Carlos and even less with William. Thus, it is likely that both new mothers would not have done as well as other new moms in identifying their babies.
Experiments are informative, but they do not mirror the real-life presentation by hospital staff of babies to their new mothers, who accept that baby as belonging to them. No one offers multiple babies for mothers to compare, so how does a mother know that a baby is truly hers?
A test comparing the DNA markers of a mother and her putative child can determine whether a woman is, or is not, the child’s mother. That is because half of a child’s DNA comes from its mother, so if the test finds no matches among the markers, the child must belong to someone else. Something similar happened in Switzerland in the 1940s, in the switched-at-birth twin case involving the French-speaking Joye family from Fribourg and the German-speaking Vatter family from Freiburg. DNA technology had not been developed then, so the testing consisted of comparisons of a series of blood types of parents and children, but the principle is the same. An Rh subgroup, originally called C, but now known as O, was especially informative in the case of the exchanged Joye twin from Switzerland. The nontwin child switched with one of the Joyes’ identical twin sons had blood type labeled cc, but since Madeleine Joye had type CC, she could not have been his mother. However, her CC type was compatible with the switched twin, who had group Cc, because Madeleine Joye could have passed on her C gene, and her husband, who was cc, could have transmitted his c gene. But matching does not prove that a man or woman is the actual parent because other people can have that same blood type. Of course, establishing maternity or paternity involves comparing more than one blood group or one DNA marker.18 The correct Joye twins were eventually identified by reciprocal skin grafts, as I explained earlier.
Fingerprinting of mother and baby upon delivery and discharge is a reliable and cost-effective practice for linking mothers and newborns, and some countries have actively promoted this practice. In contrast good impressions of footprints are harder to obtain, and, more important, infant growth precludes comparison of earlier and later images. Some hospitals have used more sophisticated methods for pairing mothers and newborns, such as radiofrequency identification devices. These consist of matching electronic tags that are inserted in bracelets worn by mother and baby and are used to monitor and record feedings, baths, and other activities. At the time of discharge hospital personnel compare the two tags to be certain that they match, but critics have argued that the bracelets are problematic because they can be removed.19 In the United States medical facilities have used a variety of procedures for ensuring that the right mother goes home with the right baby.
All this raises questions of vital importance: How accurately would mothers recognize their babies if they had no previous exposure to their own baby or to other babies? And how confident would they be in their judgments? If they answered without hesitation that a child was theirs, what would be the basis of that judgment? I suspect that most mothers would not question their relatedness to a child that a nurse delivered to her room because they have no precedent for maternity uncertainty. I also suspect that we will never know the answer to these questions because posing them to new mothers would create unnecessary worries and harmful doubts in their minds just as the mother-infant bond was about to begin.
Both Colombian mothers were recovering from caesarean surgery and had older children to care for at home. They had more to think about than the rare chance that one twin discharged to their care might belong to someone else. Like most mothers, it never crossed their mind.
Fathers have more to worry about than mothers when it comes to knowing who their child is. Because of the key features of human reproduction (concealed ovulation, internal fertilization, and continuous female sexual receptivity), men can never be completely confident that a son or daughter carried by their spouse or partner is truly theirs. This makes paternity uncertainty of great interest, not just to evolutionary psychologists (who study the cues men use to assess true parenthood), but also to attorneys (who manage lawsuits about child custody and support when parenthood is disputed) and fathers (who worry about their lack of resemblance to a particular child and a partner’s infidelity).
Paternity uncertainty is also of interest to clever entrepreneurs, such as the former health care marketer Jared Rosenthal. Rosenthal operates a thriving New York City mobile DNA testing lab. With the question WHO’S YOUR DADDY? painted in large letters across two trucks that he drives around the city, fathers questioning their relatedness to their children, as well as individuals searching for or doubting their relatedness to parents and siblings, come to him for testing. Rosenthal maintains contracts with ten thousand companies for drug tests, DNA tests, and background checks. He does the DNA testing from the privacy of his two trucks, as well as his two clinics, one in Brooklyn and the other in the Bronx.20 If Carmelo ever doubted his relatedness to William, he never said so. The man who was Carlos’s childhood father had abandoned his family and, as far as we know, never questioned his paternity of the three children he left behind. However, the greater tensions he experienced with Carlos than with the other two children, who were his biologically, could have had some roots in his sense of differences between him and his son, creating doubt about their connection.
Upshot
If Luz had been around when the switch was discovered, she might have mourned the reduced financial status that caused her to deliver her twins in one of Bogotá’s public hospitals, rather than the more desirable public clinic where she had delivered her daughter. Ana most certainly regretted the health issues that had forced her to deliver her twins in the community hospital in Vélez, especially because all but one of her other children had been delivered at home. But had she delivered her twins at home, one or both of her premature infants might not have survived.
Chapter 9
Different Versions of the Same Song
When the separated British twins Dorothy and Bridget met for the first time, they were avid readers of the same books, especially the historical novels of Catherine Cookson. More interesting was that one twin came from an intellectually stimulating home, while her sister did not. But the less advantaged sister loved to read and used a library card to obtain reading materials on her own, essentially creating her own environment from the choices around her. We all do this—which is why researchers talk about genetic influences on the environment.1
As Jorge observed, kids in La Paz had to fight harder than kids in the city to get what they wanted. Coming from a home considered lower middle class, he and his accidental brother were not wealthy, but their mother insisted that they get a good education. Both benefited from the rich educational and occupational opportunities in Bogotá, while the other brothers’ exceedingly limited choices meant that they indeed had to fight harder to get ahead. The chance separation of the two identical twin pairs into such extremely different environments created an ideal setting for comparing self-esteem, job satisfaction, and general ability among the various pairs.
Self-Esteem
Self-esteem is the degree to which one sees one’s abilities, talents, and worth positively or negatively.2 High sel
f-esteem has been linked to happiness, likability, and assertiveness, whereas low self-esteem has been associated with depression, delinquency, and aggression.3 Genetic factors account for about 21 to 49 percent of the differences among adults from all male and mixed-sex samples.4
The self-esteem scores for all the twins were extremely high, higher than those of individuals in other South American countries and the United States.5 Anticipating that some or all the twins might experience emotional difficulties because of their traumatic discovery, the television producers of Séptimo Día offered to pay for psychological counseling. But it seems that this assistance was not needed: Carlos attended just one of his three sessions and used it to sort out his girlfriend problems, and William had the constant support of his cousin, godmother, and girlfriend. It is also possible that the attention they received from the media and everyone around them offset the difficulties resulting from learning about the switch to some degree and enhanced their self-esteem. Cab drivers recognized them and took their pictures, and Facebook fans celebrated them and were eager to visit them. It is also possible that each twin’s newly discovered relationship and rapport with his identical brother raised his feelings of self-worth to some extent.
The twins in both identical pairs were quite alike in self-esteem, although the scores of Jorge and William were a little closer than those of Carlos and Wilber, but the biggest difference was between the accidental brothers from La Paz. Wilber’s slightly lower self-regard may have partly reflected his role as his accidental brother’s employee at the butcher shop, especially because these two rarely agreed on work-related issues or just about anything else. But the other accidental brothers were quite alike, probably because each could act on his own interests and they charted paths that did not cross.
The Twins at Work
Everyone enjoys long lunches, but that’s not what is at the heart of work. Instead, jobs provide two types of satisfaction: intrinsic satisfaction, such as from fulfilling personal values and interests by having the chance to be creative, and extrinsic satisfaction, such as the gratification derived from working conditions that include long coffee breaks. Genetic influence on intrinsic satisfaction is relatively modest at 32 percent, but genes have little influence on extrinsic satisfaction.6 Differences among people in how much they value creativity on the job is expected, so it is not surprising that intrinsic satisfaction shows a mix of genetic and environmental influences. However, everyone enjoys a friendly work environment, long vacations, and a pleasant boss, so the absence of genetic effects on extrinsic satisfaction also makes sense. It is also possible to look at overall satisfaction with one’s job as reflecting a combination of genetic and environmental influences.
The job satisfaction levels of the Colombian twins were as ordinary as they were extraordinary. Like most people, all four twins expressed higher intrinsic than extrinsic satisfaction, but their general satisfaction either equaled or exceeded that of other twins and nontwins, which is unusual. This was surprising because none of the four had achieved his final career goals.
Jorge was dividing his time between working at the Strycon Company, designing lines for the transport of water and gas, and going to school. He was studying mechanical engineering with the goal of working in the field. William was the full-time manager of a butcher shop and a candidate for the La Paz city council. He dreamed of going to law school someday. Carlos was an accounting analyst by day and a student of public accounting by night. He planned to study international financial standards later in the year and perhaps advance to financial coordinator. Wilber worked mostly at the butcher shop managed by William, but also at other butcher shops in town. Previously, he had installed Internet and television services for Telex-Claro, a position he regarded as his “main job.” He hoped to acquire various businesses in the future, but had no firm plans for doing so.
All four twins seemed quite satisfied with their working conditions; this may reflect their youth and adaptability, as well as the knowledge that their work situations were still temporary. The personal satisfaction they derived from their work is more interesting because the spread among them on this measure was greater. The accidental brothers from Bogotá had the highest scores here, which were much alike, whereas the accidental brothers from La Paz scored lower on personal satisfaction, but also close to one another. This makes sense because Jorge and Carlos chose to do what they were doing and could see their goals in sight, while the others did their jobs more out of necessity, and their futures were less clear. The politician in William seemed stifled behind the meat counter, although he did his best to charm his clients while serving them. Wilber did not love his job at the butcher shop, except for the freedom to manage his own time; he hoped to run his own business someday because bosses “work less and are better rested.” Experience has also taught him that in La Paz you can get a job without studying, but in Bogotá you can study and still not get one.
Brains Reared Apart
Identical twins do not have identical brains because many factors affect brain development, some in unknown ways. Magnetic resonance imaging (MRI) techniques show that identical twins’ brains can differ in volume, structure, and cortical thickness. In fact, heavier birth-weight twins tend to show greater cortical surface area, which is the folded gray matter associated with consciousness. And researchers have identified thousands of variations or changes in just thirty-six nerve cells, so it would be very unlikely for identical twins to show exactly the same variations. It is, therefore, striking that reams of studies show that identical twins’ IQs, or intelligence quotients, are more alike than those of fraternal twins, full siblings, and parent-child pairs. The average IQ difference between identical twins is six points, although some twins differ by more and others do not differ at all. The average IQ difference between fraternal twins is about ten points.7
By now genetic influence on general intelligence, about 50 to 75 percent, has been well established so that only the diehard champions of environmental influence would disagree. But what it means is that the genetic influence on intelligence is widely misunderstood. To say that mental ability is partly genetic in origin does not mean that people cannot get better at what they can do or acquire skills they formerly did not have, because everyone can improve with practice and training; it does mean that we cannot all be the same.
Studies have consistently supported the finding that years of schooling boosts IQ, on the order of about one to two IQ points per year. When identical twins are raised apart, the one with the better education usually does better on tests of intelligence, but genes still matter because identical twins in the same pair usually end up scoring closer to each other than they do to twins in other pairs.8
Before we arrived in Bogotá, the four Colombian twins took the Spanish version of the Wechsler Adult Intelligence Scale-IV, known as the WAIS-IV. All were tested on the same day so they could not discuss questions and answers. Only two examiners were available, so we insisted that each tester remain unaware of the relationship of the two individuals she would test. As a further precaution neither examiner tested the real twins because we had assigned one twin from each set to each examiner.
All four twins were curious about what the tests were for because we had kept the purpose of the test hidden—we didn’t want them to start studying or begin thinking about who might be the smartest of the bunch. One tester called William a dreamer because he asked more questions than the others, “like a child who wants to know everything.” All our twins appeared motivated, especially Carlos, who was in a hurry but still did his best, managing to outscore the other three, while Wilber had the flu, a factor that might have affected his performance. And William, always gracious and kind, turned to his examiner and said, “God bless you,” once he had completed his test.
Levels and Shapes, Highs and Lows
General intelligence information is sensitive and personal, so we can report only the levels and shapes (“ups” and “downs”) of the ability prof
iles, but they were just as fascinating as the twins’ overall scores. Ability profiles capture each twin’s strengths and weaknesses across four areas tapped by the WAIS-IV, namely, verbal comprehension, perceptual reasoning, memory, and processing speed.
Each city-raised twin mostly scored higher than, but sometimes similarly to, his country-raised twin brother across the four measures. Nothing is intellectually significant about being raised inside or outside a big city, except for the kinds of opportunities available and one’s ability and motivation to take advantage of them. Both La Paz brothers had left school when they were eleven, although William eventually completed a high school equivalency course, whereas the Bogotá brothers were pursuing college degrees. This is an extreme difference, with years of schooling one of many factors associated with test performance. And the causal connection between the two is unclear, because we can ask if brighter people stay in school longer or if longer schooling makes you brighter.9 Of course, the La Paz brothers did not have a choice about staying in school because their parents could not afford to send them. If William had had a choice, he would have stayed in school, whereas Wilber probably would not have.
Jorge’s and William’s ability profiles show some similarities, but their verbal comprehension scores diverge. Carlos and Wilber show a somewhat closer pattern, except for Wilber’s high memory score; their more similar pattern is somewhat more consistent with findings of genetic influence on the shape of ability profiles—identical twins are more alike than fraternal twins, even from a young age.10
The difference in overall ability between the unrelated brothers raised in Bogotá was typical of the difference between full siblings, while the difference between the brothers raised in La Paz was more typical of identical twins. Carlos’s education may have amplified his natural abilities and motivation, whereas Wilber (and William’s) lack of schooling seemed to have reduced their scores by a similar degree. The ability profiles of the two accidental pairs show both similarities and differences in shape, whereas the performance of one pair of replicas (the twins from each pair who were not raised together) was a real surprise. Jorge and Wilber differed considerably in level and in shape, as expected for people who share neither genes nor environment, but Carlos and William, while different in level, were quite alike in their profile pattern. This result, which is probably a chance finding based on the tiny sample of two, comes with the warning that we should only base firm conclusions on many pairs.
Accidental Brothers Page 23