article: Some find them unnerving and even slightly creepy while, to others, they are endearing, mysterious and charming. Whatever your view, one thing’s for certain: when it comes to twins, particularly identical ones, they are an endless source of fascination. Yet, despite all this interest, the rest of us remain baffled, emotionally and scientifically, by the uncanny bonds identical twins share. Having spent a year researching twins for my new novel, I have come to realise that we are only beginning to grasp how strange they truly are and quite why they have compelled us for thousands of years. Ashley (left) and Mary-Kate Olsen (right) are two of the most famous twins in the world and despite their very similar appearances they are not actually identical twins . Take pre-colonial Brazilians, who thought twins were a product of adultery, resulting in the poor innocent mother often being executed for her supposed infidelity. Some primitive African societies abhorred twins because of the way multiple births resemble an animal’s litter. It wasn’t uncommon for the unlucky children to be slaughtered and their mother exiled. In Greek mythology, however, twins were believed to be the product of human intercourse with the gods, meaning they were sacred, while ancient Slavs maintained that twins shared one special soul. Not all monozygotic twins (i.e. twins born from a single fertilised egg) are truly identical. Some are ‘mirror image’ twins. This means that in one twin the hair might swirl clockwise, in the other twin it will swirl anticlockwise — but it will swirl in exactly the same way. For one twin, the left side of the mouth might curve upwards; in the other twin, the right side of the mouth has precisely the same curve. This peculiar ‘looking-glass effect’ extends to the positioning of internal organs. But many identicals are truly identical in ways we are still uncovering. Obviously, identical twins share facial characteristics and body shape. But they also share virtually identical DNA, meaning they are more closely related to each other than to anyone else, including their parents or their own children. Joel (left) and Benji Madden (right) are identical twins, it's likely that they will have grown more alike over time as their identical DNA asserts itself . A daring £5 million jewel heist was carried out at a Berlin department store in 2009. Closed-circuit TV showed one of three masked man removing a glove at the scene, which the police later recovered. The glove provided DNA evidence traced to identical twin brothers. But with no way of pinning it on one brother, both were acquitted. Identicals also share the same blood group, the same hormones, the same serum proteins; they are alike in heart rate, blood pressure, brain waves, respiratory rate and digestive process. Hospitals in America in the past have advised parents to discreetly tattoo one twin — with a tiny dot, or mark on a heel — so that in future the children can be differentiated. Parents often refuse, believing they will be able to distinguish their twins as they age (not least, by dressing them differently). This, however, can be a mistake because twins can grow more identical over time (as their identical DNA asserts itself, following different levels of nourishment in the womb). And twins often end up being dressed in exactly the same clothes anyway, lest one become jealous of the other getting ‘better’ treatment. Here, we enter the peculiar world of twin psychology. Over recent decades, scientists such as Thomas Bouchard, of the Minnesota Centre For Twin And Family Research, have analysed the personalities of twins and discovered seriously uncanny facts. Take the classic example of twins separated at birth. The extent to which they can echo each other in later life is breathtaking. One of my favourite cases is the separated twins who discovered, when reunited, that they both entered the sea on beach holidays by wading backwards up to their knees. Probably the most famous case of eerie identicality is that of Jim Lewis and Jim Springer. These identical American twins were separated when four weeks old, and adopted by different families in Ohio. When reunited at the age of 39, in 1979, they discovered that both of them suffered from tension headaches, both had worked as sheriff’s deputies and both smoked Salem cigarettes. Hunter (left) and Scarlett Johansson (right) are fraternal twins and so do not share the same strong characteristics and traits as identical twins do . They also drove exactly the same kind of car and both enjoyed woodworking in the garage. Both had been named James by their respective adoptive parents, and both had married twice — first to women named Linda, then to women called Betty. Both had produced sons named James Allan. Both had at one time owned dogs named Toy. And they both took their holidays at the very same beach in Florida. Some parents of twins have reported their children having identical dreams. Others recount twins suffering pains, in the same part of the body, when only one of them is hurt. Doctors who observe twins in the womb have watched identicals do a strange kind of matching twin dance: the fetal twins come close to each other, face to face, then one of the twins makes a circle, and the other does the very same. It as if they are, in utero, telepathically aware of each other’s movements. Even in death, twins share an incredible bond. A prime, if rather dark, example is the 72‑year‑old brothers in Finland. In 2002, they were killed on their bicycles on the same road in Northern Finland in two accidents, two hours apart. When one twin survives the death of another, they likewise possess an oddness which startles. Author Joan Woodward, in her 2009 study of twin bereavement, reported several striking examples of twins’ reactions when one of them dies. Some young twins simply do not believe the death, and continue to act as if the lost twin is alive, talking to the dead sibling at breakfast, in a shared twin language, for instance. John and Edward Grimes, commonly known as 'Jedward', are identical twins. Some parents of identical twins have observed them having identical dreams or even suffering pain in the same parts of the body . Other infant twins seem painfully confused as to whether their twin is really gone, because they keep seeing the living image of their dead sibling in the mirror or in a reflecting window; when they see themselves, they see the sibling. By contrast, a few bereaved twin children deliberately seek out mirrors in order to reassure themselves their dead twin lives on. They want to see the living ghost. Other twins react differently still. Woodward records how some, following the death of a co-twin, take over their lost sibling’s characteristics and behaviour, as if trying to make up for the loss by actually becoming the dead sibling. One twin whose brother died at the age of 12 became so eerily like his dead sibling that his parents were convinced he had the ‘spirit of his brother within him’. Another female twin was so grief-stricken she took her dead sister’s name. These strange reactions surrounding the deaths of identicals can have effects beyond the twins themselves. During my research, I came across one wholly remarkable example of twin confusion, following a death. It happened in California in the Nineties (though the details and names have been protected by the authorities, for obvious reasons). One day, driving off on holiday, the Andersons — father, mother and their identical twin daughters Samantha and Katie — had a terrible crash. An ambulance was called and the victims were cut from the car. However, after reaching the hospital, Samantha soon died and Katie was left in a coma. It was a horrific loss, but life had to go on. The family concentrated on helping the hospitalised Samantha get over the death of her twin. A funeral for Katie was held. And yet, as her surviving daughter improved, mum Sally found it strange that Samantha behaved so much like her dead sister. Finally, Sally studied her child’s birthmark very closely (the twins had similar but not identical birthmarks) and realised a terrible mistake had been made — Katie had survived and Samantha had died. This realisation occurred two weeks after the accident. The Andersons had buried the ‘wrong’ daughter. It was reading that extraordinary true-life story — and all these other facts — that gave me the idea for a thriller. What would happen if the Andersons’ experience was repeated, but the family only discovered their error a year later? What ghostly consequences might ensue? Whatever the answer, one thing I know for sure is that twins will continue to fascinate us because they pose so many profound and unsettling questions. S. K. Tremayne’s The Ice Twins is published by HarperCollins.
highlights: Pre-colonial Brazilians thought twins were a product of adultery .
  Greek mythology believed twins were the product of intercourse with gods .
  Many of us remain baffled by the uncanny bond identical twins share .
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