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A THING OR TWO ABOUT TWINS

By Lungile Lulane | 2018-03-18

With so many twins among us these days, it’s high time we celebrate some of the most interesting facts about them. Here are 11 facts about twins that make them even cooler than you already thought.

Identical twins do not have identical fingerprints.

You might think that because identical twins supposedly share almost the same DNA, they must also have identical fingerprints. Well, that’s not true. Fingerprints are not solely generated based on DNA. When identical twins are conceived, they start out with the same fingerprints, but during weeks six through 13 of pregnancy, as the babies start to move, they each touch the amniotic sac, and unique ridges and lines are formed on each twin’s hand that result in different fingerprints.

Mirror image identical twins have reverse asymmetric features.

About 25 percent of identical twins develop directly facing each other, meaning they become exact reflections of one another. According to About.com, “they may be right- and left-handed, have birthmarks on opposite sides of their body, or have hair whorls that swirl in opposite directions.” This occurs when the twins split from one fertilized egg more than a week after conception.

Identical twins do not always have the same genetics.

While identical twins derive from one fertilized egg that contains a single set of genetic instructions, also known as a genome, it’s still possible for identical twins to have serious differences in their genetic makeup. Geneticist Carl Bruder of the University of Alabama at Birmingham closely studied the genomes of 19 sets of adult identical twins and found that in some sets, one twin’s DNA differed in the number of copies of each gene it had. Normally, every person carries two copies of every gene, one inherited from each parent, but Bruder explains that there are “regions in the genome that deviate from that two-copy rule, [and] these regions can carry anywhere from zero to 14 copies of a gene.

Mothers of twins may live longer.

A study published in the journal Proceedings of the Royal Society B focused on the population of women in 1800s Utah and found that women who gave birth to twins were very strong and healthy to begin with, so were likely to live long lives. As LiveScience writer Stephanie Pappas explains it, “Twins could be an evolutionary adaption in which healthy moms take the chance to pass on double their genes at once.”

However, because the data only includes women who conceived twins naturally — IVF was obviously not used in the 1800s — the findings are not definitive.

Tall women are more likely to have twins.

Gary Steinman, MD, PhD, an attending physician at Long Island Jewish (LIJ) Medical Centre, discovered that taller women have more insulin-like growth factor (IGF), a protein that is released from the liver in response to a growth hormone that stimulates growth in the shaft of longer bones. Having higher levels of IGF results in increased sensitivity of the ovaries, thus increasing a woman’s chance of ovulating. According to Steinman, the more IGF a woman has, the greater chance she has of becoming pregnant with twins, because IGF “govern[s] the rate of spontaneous twinning.”

Also, women who eat a lot of dairy are more prone to conceiving twins.

Another study done by Steinman and published in the Journal of Reproductive Medicine found that women who eat more dairy products may increase their chances of conceiving twins. Steinman tested this by comparing twin rates from vegan mothers and non-vegan mothers. Those who consumed dairy were five times more likely to have twins. This is because cows, like humans, also produce IGF in response to growth hormone and release it into their blood. Then it gets released into their milk, which women consume.

Twins interact with each other in the womb.

In 2011, researchers at Umberto Castiello of the University of Padova in Italy studied 3D videos of twins in their mother’s womb. At 14 weeks of gestation, twins were seen reaching for each other. By 18 weeks, they touched each other more often than they touched their own bodies. The researchers said that kinematic analyses of the recordings revealed that the twins made distinct gestures toward each other and were as gentle to the other twin’s delicate eye area as they were when they touched their own.

Some conjoined twins can feel and taste what the other one does.

Susan Dominus wrote a piece for The New York Times about two conjoined twins, Krista and Tatiana Hogan, who are attached at the head through a “thalamic bridge,” part of the brain that acts as a sort of “neural switchboard” and filters most sensory input. Scientists have hypothesised that this connection could result in one Hogan sister being able to taste and feel what the other twin is experiencing and to understand each other’s thoughts. Dominus, who spent a considerable amount of time with the twins for her story, recorded these amazing observations:

9. Forty percent of twins invent their own languages.

These languages are called autonomous languages. Researchers suspect that twin babies use each other as models in developing language when an adult model language is frequently absent. The “language” consists of inverted words and onomatopoeic expressions. These autonomous languages are formed when two very close babies are learning how to speak a real language alongside one another and naturally often play and communicate with each other. While this is more common among twins, since they are more likely to be around each other and developing at the same rate, this phenomenon can also sporadically occur between two babies who are not twins.

The made up “languages” often disappear soon after childhood, once the children have learned a real language.

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