Twofold

Loss of a Twin

Nancy L. Segal — Mon, 27 Jul 2009 22:50:47 +0000

Twin Loss: The Annual Convention

The Twinless Twins Support Group International (TTSGI) was founded in 1984, by Dr. Raymond Brandt. Its annual conventions allow dozens of twins to share their life stories with those who fully understand the nature and level of their grief. Many TTSGI members have participated in the ongoing Fullerton Twin Loss Study, research that began at the University of Minnesota in 1985. Some twins from the Australian Twin Register have also taken part.

I attended the July 2009 Twinless Twins Convention, held in Denver Colorado. This meeting drew dozens of bereaved twins and some parents of twins together for a weekend of important and memorable moments. Highlights from two events (the keynote address and twin testimonials) follow a selected sampling of research findings on twin loss. Note that the original article and references will be published in the next issue of TWIN RESEARCH AND HUMAN GENETICS.

The Research

Two key findings have emerged from the extant research on twin loss. The first is that identical twins experience the loss somewhat more intensely than fraternal twins, although there is considerable overlap--the loss experience may be just as devastating for some frasternals. There is also evidence of less grief reduction over time for identical than fraternal twins, on average . The second finding is that the loss of a twin is associated with greater grief than the loss of any other relative, with the exception of a spouse. This make sense in evolutionary terms—in the absence of a partner, one cannot transmit genes to future generations. At the proximal level, spouses are the people chosen to be lifelong companions. Interestingly, grief associated with spouse loss did not differ from grief associated with twin loss. Comparing the effects of twin loss versus spouse loss between surviving MZ and DZ twins would be revealing; however, my own sample of nearly 700 bereaved twins does not include sufficient numbers to support such an analysis. In addition, very few twins (fortunately!) have lost children, also precluding twin group analyses of such data.

Loss of a twin either before, or shortly after, birth can profoundly affect surviving twins. Biographies of well known figures, such as science fiction author Philip K. Dick and rock n’ roll star Elvis Presley include references to the missing twin in childhood and adulthood. Joan Woodward has studied such cases, but research in this area is clearly wanting. A timely issue concerns the emotional responses of adult individuals whose co-twins were selectively terminated, following the successful implantation of multiple embryos. I am unaware that such research has been done.

Suicide survivors constitute a special subgroup of surviving twins. They are a valuable research group because they enhance understanding of the nature and origins of suicidal behavior. My own research, in conjunction with Dr. Alec Roy, has indicated a higher frequency of suicide attempts among identical than frtarenal twins whose co-twins had suicided. They also found that suicide attempts occurred with very low frequency among both types of twins whose co-twins’ death were non-suicides. These results are consistent with genetic effects on suicidal behavior.

Danish investigators reported a reduction in suicide among both identical and fraternal twins, relative to non-twins. The interpretation was that twins provide social support for one another, offsetting any risk. Another Danish team) found that survival is improved by having a spouse, friends and a co-twin. Contact frequency was a significant factor in the survival of women and MZ twins.

Finally, the coping process of some twin suicide survivors can be complicated because they cannot express anger at a person or event for causing their twin’s death. This reaction was expressed by several twin suicide survivors at this year’s Twinless Twins convention.

The Convention

Te first address of the morning was by New York City clinical psychologist Mary Morgan. She was ideally qualified to do this, given her professional background and the fact that she lost her twin brother at the age of twenty-one. She mentioned the immediate connection she felt with the group when she first joined.

Several key themes were touched upon in her talk. One was the extreme loneliness that twins feel when they lose their co-twin. Everyday reminders (e.g., a song or a smell) can reawaken the fact that the twin is no longer present. Another theme was the uniqueness of each person’s recovery process. People cope with their loss in individual ways and according to individual timetables. A final theme was the lack of understanding that some family members may unknowingly display toward bereaved twins. The process of recovery may take longer for twins than for non-twin relatives who can become impatient with twins’ enduring grief. All these themes have emerged from the Twin Loss Surveys completed for the Fullerton Twin Loss Study.

Mary Morgan should be applauded for her efforts on behalf of the twin survivors of the World Trade Tower attack. She organized a support group for several of the New York City twins for many months in the aftermath of that tragic event. Additional information about her work can be found at www.twinlesstwins.org. A biographical sketch of one such survivor is included in my book, Indivisible by Two: Lives of Extraordinary Twins.

The second part of the day was dedicated to twin testimonials. Twins were invited to describe the circumstances of their loss, its effects on their life, their methods for coping and their fondest memories of their twins. These sessions were extremely moving and gave depth and substance to the data files that others and I have amassed over the years. Each life story was a different take on the emotional difficulties and complexities that bereaved twins face. Teenagers mourned the fact that they would not experience this crucial life stage with their twin. Young adults worried about the well-being of their nieces and nephews (their co-twin’s children). Older twins, even those whose twins had died many years before, emphasized the unreality of their loss. Many told me privately that one never fully gets over the loss of a twin, which may explain why some twins return to the convention year after year. It was observed (ironically) that TTSGI’s members are highly dedicated to the organization, even while they would prefer to be non-members.

Twin researchers are in the fortunate position of producing findings that are meaningful at both theoretical and applied levels. Closer personal contact between researchers and twins has enormous benefits for everyone. It provides twins with information and guidance, and offers researchers ideas and topics for future study.

Triplets--An Unusual Case

Nancy L. Segal — Wed, 15 Jul 2009 23:16:53 +0000

This article is reprinted, in part, from a longer one in a recent issue of the journal Twin Research and Human Genetics.

A mother of young identical male triplets described a harrowing pregnancy that included bloating, spotting and a fifteen-week diagnosis of triplets with cleft lip (all three boys) and cleft palate (one boy). Each baby’s cleft was in a different location, and each showed the trait to a differing degree. Their geneticist informed the family that this was the world’s first case of identical triplets with cleft lip/palate.

Cleft lip and palate affect approximately 1/700 newborns and may be associated with either genetic or non-genetic factors. DNA testing revealed that the triplets did not have the genetic variety; in fact, the origin of their clefts is uncertain

Breast-feeding poses considerable challenge to higher order mothers of multiples. It was even more difficult in the case of the young triplets. In an informative and moving essay, their mother recalls the frustration and determination that made breastfeeding her boys possible. Initially, she was unable to obtain information as to the feasibility of breast-feeding her children, either from physicians or from other parents. Still in the hospital, she attempted unsuccessfully to pump her breast milk, despite discouragement from a nurse who implied that such efforts would be “fruitless.” Meanwhile, the babies were being fed small amounts of a sugar solution.

She returned home, leaving the premature triplets in the hospital. Another nurse (also a mother of twins) advised her to place a photo of the boys in front of her and to try again. This time it worked, and she began a regimen of pumping and delivering the milk to the hospital at regular intervals. Then, prompted by a lactation consultant, she attempted to actually breast feed the babies. This proved impossible for the baby with cleft lip and palate since he could not create the necessary suction; he continued to receive the pumped milk. However, the process worked beautifully with the other two boys. When they reached twenty-two months of age, all three had surpassed their developmental milestones.

This family’s experience is important for researchers, parents and physicians to hear. When I interviewed her she spoke again about the time that she was first able to pump milk. She wonders whether the photograph of the boys may have triggered maternal feelings that allowed the milk to flow. I asked her why other parents were not helpful in this regard; she believes that they were discouraged from trying to breast feed their children as she had been. Furthermore, she was not allowed to touch the babies until three hours after they were born, compounding her difficult situation. Touching them would have created stimulation, causing them to burn calories.

The triplets’ clefts have been surgically repaired and are hardly noticeable in two of the boys. The three are terrific friends, and while they fight occasionally they quickly defend each other if anyone comes between them. When they start school next year they will be I the same class and play on the same hockey team.

DNA Dilemmas: New Riddles from Twins

Nancy L. Segal — Sat, 21 Mar 2009 23:01:36 +0000

Identical twins’ shared DNA has led to some extraordinary dilemmas when it comes to assigning paternity or assigning blame. For example, I am aware of several cases in which women have had sexual relations with both members of an identical males twin pair, such that the biological father of their children cannot be identified. Strangely, the identity of the child’s maternal grandmother (the twins’ mother) is certain! Such situations can place unusual strains (and limits) on legal decision-making.

A different sort of case poses the same uncertainties. There was a recent robbery at Kaufhaus des Westens (KaDeWe), a famous Berlin department store. KaDeWe happens to be the second largest store in Europe after Harrod’s. Watches and jewelry, worth up to 100,000 euros, were stolen. However, some clues were left behind. A rope ladder and a glove provided investigators with DNA that they hoped would help them find the three suspects. It turned out that one DNA sample was linked to two people—identical twins, Abbas and Hassan O. Now each twin can claim that his twin brother had committed the robbery. It will be fascinating to follow this case as it unfolds.

Strictly speaking, identical twins may not share 100% of their DNA. For example, co-twins may show copy number variations (CNV), i.e., altered DNA sequences that can happen due to mutatiosn, deletions or other processes. CNVs may be responsible for some inherited diseases, so they are a focus of great research interest at the moment. However, the technology to identify a twin father or a twin criminal by means of CNVs is currently unavailable.

There are other relevant situations of interest. One member of an identical male twin pair was born with anorchia, a condition in which one or both testicles are absent at birth. However, the co-twins agreed to a testicle transplant—and the recipient twin was able to father children. Ovary transplants have also occurred successfully between identical twin women. Parents of such children would be genetically indistinguishable. In fact, when ordinary identical twins marry and have children, the twin parent and twin uncle or aunt share the same genetic connection to their child and niece or nephew. Perhaps the most gratifying case was documented in my recent book, Indivisible by Two. An infertile female twin became a mother twice—because her twin sister was artificially inseminated with her brother-in-law’s sperm. The children that resulted were as biologically related to their parents as if they had conceived them naturally.

More Octuplets: Combinations and Permutations

Nancy L. Segal — Fri, 13 Feb 2009 18:13:12 +0000

Multiple births are a great addition to research addressing genetic and environmental influences on behavior. It occurred to me that the new octuplets offer some amazing possibilities: The eight babies include:

28 twin pairs

56 triplet sets

70 quadruplet sets

56 quintuplet sets

29 sextuplet sets

8 septuplet sets

They also offer an amazing array of identical and fraternal pairs, as well as same-sex and opposite-sex sets.

Why Some Identical Female Twins Are Different

Nancy L. Segal — Mon, 09 Feb 2009 21:38:53 +0000

Behavioral and physical differences between identical twins are fascinating because they are unexpected. Many people assume that when identical twins differ they do so because they are treated differently by others, or because they try to differentiate from one another in order to carve out a separate identity. These explanations may all be true at some level-but it is important not to overlook a hidden, yet powerful source of difference between identical female twins: X chromosome inactivation.

X chromosome inactivation is a process that affects all females, not just twins. Very soon after conception, one of the two X chromosomes in each cell shuts down. One X chromosome is received from the mother and one X chromosome is received from the father-and which one becomes inactive in a given cell is a matter of random chance. Typically, half the X chromosomes from mom and half from dad are inactive, which also means that half from each parent are active. If the X chromosome from dad carried the recessive gene for color-blindness, the daughter would still have normal color vision if she inherited the dominant color vision gene from mom. However, things do not always work out that way. If there were skewed X-inactivation (meaning that a high proportion of Dad's X chromosomes were active), then a daughter might express the color-blindness trait.

This process has some curious consequences for identical female twins. If the twins result when the fertilized egg splits very early after conception and before X-inactivation take place, then the twins may differ in traits located on the X chromosome. This is exactly what happened in a case report I came across recently.

Bennett, Boye & Neufeld (2008) described a difference in hemophilia A in a pair of identical female twins. The female twins in question were born to a father who had two normal genes and a mother who carried one recessive gene for this condition and one normal gene. Medical attention was sought when one infant twin developed excessive bruising and bleeding from minor incidents. Blood studies revealed skewed X-inactivation toward the paternally derived X chromosome in this twin. In contrast, her unaffected twin sister showed random X-inactivation. This is the first reported case of hemophilia A discordance in MZ twins. Other conditions for which identical female twins have differed include color-blindness and the Lesch-Nyhan syndrome.

It is plausible that psychological differences between identical female twins might also emerge in this manner. This is another example of how twin research can add to what we know, and can know, about human behavioral development.

Bennett, C.M., Boye, E., & Neufeld, E.J. (2008). Female monozygotic twins discordant for hemophilia A due to nonrandom X-chromosome inactivation. American Journal of Hematology, 83, 778-780.

Octuplets: Views From One Who Studies Two

Nancy L. Segal — Mon, 09 Feb 2009 21:38:47 +0000

The recent birth of the Suleman octuplets in southern California has attracted unprecedented attention from physicians, parents and publishers around the world. It is a frequent topic of conversation in coffee shops and classrooms. Issues surrounding the octuplets' child care, health expenses, biological origin and future development-all important and timely--have been debated endlessly. It is worth asking: why are people following this story so closely? Aside from the concerns mentioned above, there may be other reasons why people care.

I have suggested in my recent book ENTWINED LIVES that twins, triplets and more capture attention because they contradict our expectations about the way the world should be. That is, we live in a culture that anticipates and prizes individual differences in behavior; thus, when we confront two or more individuals who look and act so similarly, it becomes intriguing. Onlookers variously view identical twins with amazement, pleasure, disdain, or even fear, but always with fascination. Perhaps identical twins' most engaging attribute is their close social relationship, characterized by complete understanding and acceptance. It is a luxury that many people envy and love to see.

Most women have one baby at a time, so that two or more births become landmark events. Deliveries of higher order multiples (three or more) are especially celebrated, despite the well-known health risks to mothers and infants. Furthermore, octuplets have been delivered successfully only one other time, ten years ago, although one of the babies died within the first week. This probably explains, at least in part, why the recent successful birth of the Suleman ocuplets has been so consuming. This birth sets a new record, and new records are always compelling.

Physicians may wonder if other women will be inspired to follow this lead, or try to surpass it, but that seems unlikely, (For example, women in their sixties can become pregnant via egg donation and in vitro fertilization, yet few elect to do so.) The challenges of child-bearing and child-rearing are well-known, magnified by higher order multiples. But we can hope that the new babies, now that they are here, will continue to thrive.

Political Pairs

Nancy L. Segal — Wed, 22 Oct 2008 20:24:10 +0000

It's the new hot topic in psychological twin research-to what extent do genes affect our interest and participation in politics? With the November election looming in the very near future, this is an opportune time to examine the research.

Studies by James Fowler at the University of California, San Diego address a host of relevant questions. It turns out that simply voting has a genetic basis. Research has shown greater similarity between identical than fraternal twins across eight different California elections. This result was later replicated using an entirely different sample, drawn from a national study.

Do genes affect the strength and direction of partisanship? Again, twin studies can help answer these questions. This time, Fowler and his colleagues solicited the participation of twins attending the annual Twins Days Festival in Twinsburg, Ohio. Twins responded to the question: "Generally speaking, do you usually think of yourself as a Republican, Democrat, or what?" The seven response categories (later reduced to four) were Strong Democrat; Democrat; Independent, but closer to Democrats; Independent; Independent, but closer to Republicans; Republican; Strong Republican.

Genetic effects were found for partisan strength, but not for partisan direction. However, non-twin research by John Alford at Rice University and John Hibbing at the University of Nebraska has found some intriguing associations between partisanship and reactions to various types of stimuli. Individuals reacting more strongly to negative stimuli were more likely to endorse conservative policies than individuals reacting less negatively. Attitudes on social policies had been assessed by questionnaires.

Politicians. Only a small percentage of individuals seek higher governmental office, so it is striking to discover identical twins holding similar positions, or showing similar levels of involvement. Identical twins, Lech and Jarowslaw Kaczynski, were President and Prime Minister of Poland, respectively. Lech was inaugurated as President in December 2005, while Jarowslaw was appointed Prime Minister by his twin brother in July 2006. Jaroslaw was later ousted by Donald Tusk from the opposition party in October 2007.

Another well-know political pair is identical twins Julian and Joaquin Castro, from San Antonio, Texas. After graduating from Stanford University and the Harvard Law School, Julian became a member of the City Council and later ran unsucessfully for Mayor in 2005. Joaquin became one of the youngest state legislators in Texas, an office he still holds. Other sets include Jerry and Terry Kilgore, and Ron and Don Mosbaugh Jerry Kilgore is the former Attorney General of Virginia. He ran for governor of that state in 2005, but was defeated. Terry Kilgore is serving his eighth terms as delegate of Virginia's first legislative district. Don and Ron Mosbaugh both ran for Jasper County, Missouri coroner in 2000. The twins shared their campaign manager, but Don ran as a Democrat and Ron ran as a Republican. Ron (the incumbent) defeated Don with a vote count of 22,859 to 13,247. (It is curious that the first letters of their first names correspond to the first letters of their party affiliations.)

No one has done a twin study focusing on political careers, but such a study would be worth doing. Note that all of the pairs cited above are identical. Fraternal twin politicians tend to serve as individuals, e.g., Donna Shalala Shalala (former Secretary of Health and Human Services) and the late Paul Tsongas (former Massachusetts senator).

It is interesting to speculate as to the kinds of characteristics that propel a person into a political career. Various combinations of civic responsibility, extroversion, stage presence, information-processing and verbal skills are most likely required. Most, if not all, of these have demonstrated genetic components. Clearly, there are no single genes for becoming a politician-but an array of genetically influenced traits, in conjunction with the right opportunities, might provide the answer. So far, the only twins to live in the White House have been George Bush's fraternal twin daughters, Barbara and Jenna. There have never been any United State presidents who were twins.

A more detailed version of this essay, including references, will be available in an upcoming issue ofTwin Research and Human Genetics, the official journal of the International Society for Twin Studies.

Twins Reared Apart--But Together Again

Nancy L. Segal — Thu, 03 Jul 2008 18:46:22 +0000

I spent the last few days at the annual Behavior Genetics Association meeting in Louisville, KY. I listened to a fascinating series of papers that used twins to demonstrate genetic influence on voting behavior, temperamental traits and problem solving. I fully intended to summarize some of these studies for my next blog--but something happened today to alter the direction of this entry. I spent the morning with Steve, a single dad, who recently adopted two-year-old Larry. It turns out that Larry has an identical twin brother Ted, adopted by another family hundreds of miles away. Watching father and son, hearing the details of Larry’s brief, but eventful life history, and enjoying the pictures of Larry with his twin brother on the two occasions that they met provided considerable material for reflection. (Note: Names and other identifying information have been altered in the interest of privacy.)

I have always believed that twins belong together, and still do. Twins meeting for the first time as adults describe anger, resentment and sadness at having been raised apart, often for the convenience of others. Most of these twins were raised in adoptive homes and while many had warm loving parents, they welcomed a meeting with a close biological relative. Over the years I have had a number of opportunities to serve as a consultant for legal cases concerning the joint or separate rearing of twins. With the exception of one rare pair involving a severely brain damaged twin, I always endorsed joint rearing. But things happen. Twin infants are sometimes separated, and the best that families can do is to bring the children together as often as possible.

A recent source of separated twins is China, where the One-Child Policy was enacted in 1979. This policy limited urban families to one child and rural families to two. Given the enormous value placed on male children in China, thousands of baby girls were abandoned and adopted by couples around the world. Among the children were separated twin sisters whose families find one another because of photographs and other information posted on websites. I have been studying these children, something I have mentioned in previous posts. But twins are separated in many places, not just in China. Larry and Ted came from another Asian nation. They lived together with their biological parents until they were five months old, then spent the next year in an orphanage and foster care facility. Ted was adopted at 13 months, Larry at 16 months. Neither family knew that their small son had a twin brother—until the families saw their photos on a website. A DNA test confirmed what everyone suspected—that the boys’ were identical twins.

I rarely see the separated twin children that I study because they live all over the United States. I have arranged for participating families to complete inventories and questionnaires by mail, and to have children undergo general intelligence testing by local testers. So it was a treat to meet Steve and Larry and to see them together. Fortunately for the twins (and for the twins in most of the other families I have studied), the parents are acutely aware of the importance of twinship and try to bring the children together often. This is not always easy, given the distances between them. This also means involving another family in everything from important decisions to summer vacations—but most parents have embraced this enthusiastically. The payoffs are considerable, mostly in the form of watching their child’s twin relationship flourish and evolve into a potentially close and caring bond.

Some people will wonder why one family did not take both twins. once twinship was discovered. This is a good question, one that has several answers. First, assignment of children to parents is done via adoption agencies and cannot be altered. Families attempting to make changes run the risk that both children will be given to other couples who may not be willing to bring the twins together. Second, the adoption process is lengthy and expensive, often lasting over a year and can cost thousands of dollars. Thus, considerable effort and sacrifice is required for foreign adoption. Third, the parents immediately fall in love with their children. The attachment between them is very strong, usually before the twinship is discovered. (This was clearly true of Steve and Larry—Steve had his eye on his son the entire time that we talked, and when Larry became upset he quieted down in his father’s arms.) To break that bond would be damaging to everyone involved. So the families do the next best thing which is to become part of one another’s lives. They should be commended for this.

As one mother told me, reared apart twins who know one another growing up are truly unusual. It will, therefore, be exciting to witness the developmental outcomes of the twins in my study as they age— Will they like the same things? Will they be friends? If they resent being apart, will they understand that it is because their parents love them?

Mistaken Identity—Twins?

Nancy L. Segal — Wed, 04 Jun 2008 22:57:03 +0000

I recently finished reading Mistaken Identity (2008), an extraordinary account of what happened to two families when the wrong daughter was identified in a fatal car crash. Both Laura Van Ryn and Whitney Cerak, students at Taylor University in Indiana, were returning home in a van with 15 other students. A terrible car accident left five of the students dead, one identified as Whitney Cerak. Laura was brought to a hospital for intensive treatment, during which time her family remained constantly at her bedside. But over the five-week course of care, the Van Ryn family eventually realized that the person in the bed was not their daughter, but someone else’s daughter—it was Whitney. It seems that the girls bore a general resemblance to one another, both being blonde and athletically built. One family suddenly grappled with a shocking loss, the other with an unimaginable joy. I thought about this book the other day when I learned of a reunion between identical twins, brought about through another kind of mistaken identity.

The reunion happened in Spain’s Canary Islands. A thirty-five-year-old woman entered a shop and was greeted warmly by the assistant who believed she was her friend. But the assistant was rebuffed. The assistant later called her friend to follow up, only to learn that her friend had never been to the shop that day. The first woman returned several days later, and it was then that the assistant began to question her. A meeting was arranged—and it was clear that the two (the woman and the friend) were identical twins; this was later confirmed by DNA testing. To complicate things further, one of the women said that she had a twin sister, but that she was not identical. Eventually, it was established that one of the twins had been accidentally switched with a non-twin infant in the hospital’s baby nursery. And it was disclosed that the identical twins had been conjoined and successfully separated, although the nature of their physical connection was not reported. Everyone’s life was immeasurably altered by that chance recognition, and the various parties are suing the hospital for millions of dollars.

Of course, this latest case reminded me of a similar one involving twins that I discuss in my book, Indivisible by Two. A set of identical male twins and an unrelated male infant were in foster care together. When two of the infants were moved to a second home, the twins did not go with one another, as planned—instead, one twin and the unrelated male were moved together The twins eventually met through mistaken identity, but it was not until twenty years later. A lawsuit was brought against the agency that had been responsible.

Not all cases of mistaken identity lead to twins, nor do they lead to lawsuits. When I was associated with the Minnesota Study of Twins Reared Apart, I encountered many twins who were brought together because someone had confused one for the other. In some cases they knew that they had been born a twin, but in other cases they did not.

Perhaps the most amazing story concerned elderly ladies who had grown up about twenty miles apart from one another, in Scotland. One day, one of them was working in the church that the other one happened to visit. The two recognized themselves in each other and cried with happiness.

I am currently conducting studies of young Chinese female twins separated at birth, an indirect consequence of China’s One-Child Policy. Many of the parents post stories and pictures of their children on adoption websites—and occasionally these postings lead to twin reunions. I was in touch with two families whose daughters looked strikingly alike in unusual ways. I was certain that they were identical twins—until the genetics laboratory informed us that they were unrelated. I mentioned this to a colleague who suggested that perhaps there is a finite (albeit, large) number of facial configurations, such that on rare occasion two people end up looking very much alike. Francois Brunelle, in Montreal, has taken beautiful photographs of some of these unrelated look-alikes, and I have a study underway to see how similar they might be.

Some people do not relish the idea of an identical other—and yet many people envy the closeness and intimacy that comes so naturally to most identical twins. A number of the reunited twins in our study had initial concerns about loss of identity or sense of self, but their worries faded fast once they got to know one another. As investigators, we were impressed with how similar the reared apart identical twins were, but it was never perfect similarity. It also surprises me that most identical twins think that they do not look alike—and yet many must if mistaken identity can bring some together.

We have no idea how many twins are out there now, searching for one another, or how many are living lives as the singletons they believe themselves to be. We will probably never know because some of them will never meet. But we will celebrate with the ones that do.

Fraternal Twins--The Hidden Pairs

Nancy L. Segal — Wed, 07 May 2008 22:55:10 +0000

I was on the Today Show today, May 7, 2008. The taped piece focused on studies from two separate laboratories. The first study concerned research on twins’ social relationships, conducted in my lab at California State University, Fullerton. In general, I have found that identical twins show closer, more cooperative behaviors than fraternal twins when working on a common task. The second study concerned new findings that identical twins may show actual DNA differences (what are called copy number variations--CNVs), conducted at the University of Alabama. Twins with DNA differences may help us understand what factors trigger illness or other conditions in one twin, but not the other. However, there were twins in that study who showed DNA differences, but who did not differ in other significant ways. These two studies are related in that DNA differences between identicals could be associated with behavioral differences; these could ultimately affect the twins’ social relationships. The two taped segments were followed by live interviews with two sets of identical twins, one male and one female. The male twins were current and past football greats, Ronde and Tiki Barber. Tiki Barber left the New York Giants last year to join the Today Show as a special correspondent. One of them commented that they do not try to do things the same way, but often end up doing them alike. As examples they cited buying the same item—and of course ,they play/played football. The female twins were my colleague, Dr. Eileen Pearlman, and her twin sister Elaine. Interestingly, Dr. Pearlman noted that as the slightly leaner twin from birth, she was referred to as “skinny”—and when she sees her twin even today she feels compelled to watch her diet to remain in that role. Both pairs also emphasized the importance of separating twins so that they feel prepared for the inevitable separations that occur later in life, e.g., school, work, marriage. I would qualify that, especially with reference to twin type. First, as indicated above, identical twins tend to be closer than fraternals and should, I feel, be allowed to enjoy their relationship. Most identical twins celebrate their twinship, emphasizing the great understanding and comfort it affords. I fully support the state-by-state movement, currently in play, that is developing legislation that would give parents a significant voice in their twins’ classroom placement. Too often, schools demand that twins be separated, when it is not in their best interests. Of course, some periods of separation for twins are needed—but in their own ways, each set will reveal what is appropriate for them. Fraternal twins may naturally gravitate toward their own friends and interests, but even they may suffer the effects of premature separation from one another. The bottom line is that the needs of each set should be handled on a case-by-case basis. This brings me to the final point. Fraternal twins are far more common than identical twins, yet the media focus on the latter. Understandably, their matched appearance makes for great visual effects. But science could not proceed without the presence of fraternal twins, that all-important control group for comparing twin similarity. (Greater resemblance between identicals than fraternals demonstrates genetic influence on the trait in question.) More families are raising fraternals than identicals and are in need of information and support, yet they and their “hidden twins” are overlooked. There are some fascinating varieties of fraternal twins that many people are unaware of—twins with different dads; twins who appear to come from different ethnic groups; and more. We also know a lot about the causes of fraternal twinning, a subject that would make for great viewing. I say this mostly as an investigator--not as a fraternal twin.