Identical twins share the same genomes and are always of the same sex. In contrast, fraternal (dizygotic) twins result from the fertilization of two separate eggs with two different sperm during the same pregnancy. They share half of their genomes, just like any other sibling
》There are more lefties among twins.
Twins have approximately twice as many left-handed individuals among them compared to other people. That's about every one in five pairs. (22% of twins are left-handed as opposed to the 10% of singletons who turn out to be left-handed.)
》Twins are also more commonly female, rather than male. But male embryos die at a higher rate while in-utero than do female embryos. The death rate is also higher for twins in-utero overall.
》About 25% of identical twins are "Mirror Image Twins"
Meaning they are exact reflections of one another. For example, if one has a freckle under the left eye, the other's freckle will be under the right eye.
》Fraternal twins are no more alike than any siblings
Fraternal twins (i.e. two eggs that got fertilized separately) can look identical or completely different, even having different skin colors. It's basically a genetic roll of the dice which genes each baby will receive from mom and dad (just like with singletons).
》Though they share the EXACT genetic makeup, Identical twins do not have identical fingerprints.
》At nearly 41.3%, Connecticut has the highest rate of twin births.
》Another and published in the Journal of Reproductive Medicine found that women who eat more dairy products may increase their chances of conceiving twins.
》Identical Twins Aren't Exactly Identical
A recent study published in the Proceedings of the National Academy of Sciences reported that environmental factors such as dietary habits and chemical exposures — also known as epigenetic effects — cause identical twins to grow dissimilar over time, according to a Live Science article. For example, identical duos may start to look less alike over the years, they can have totally different personalities, and one may wind up with a disease like cancer while the other doesn't
》Some conjoined twins can feel and taste what the other one does. This is a result of sharing a thalamic bridge
》The New York Times once published an article that stated that conjoined twins have a "neural bridge." This allows them to literally read each other's minds.
》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.
》Researchers from University of Padova in Italy recently studied 3D ultrasound videos of five sets of twins in the womb. When the fetuses were just 14 weeks old, the researchers noticed that the pairs seemed to be reaching out for each other, touching head to head and arm to head. At 18 weeks, they were stroking each other more often and were in physical contact about 30 percent of the time.
》About 40 percent of twins actually develop their own language, according to researchers. When twins mimic each other's babbles instead of their parents' speech, it's called idioglossia or cryptophasia.
》Twins who get separated at birth, totally unaware of each other's existence, often lead bizarrely parallel adult lives.
"Jim Twins," according to Live Science, two separated twins who somehow both got named Jim. When they met as adults, they'd each been married twice — their first wives had been named Linda, and second wives named Betty. Weird, right? Both grew up in Ohio, were chain smokers, and drove similar cars.
》Dogs can tell the difference between identical twins.
In a 2011 study published in the journal PLOS One, German shepherd police dogs were presented with the scents of identical twins. Then, they were then able to find the exact matches among jars that contained scents from other people that were meant to distract them. Though the dogs were already trained to track down individual scents, according to the report, they were able to pick out twins "even if they live in the same household and eat the same food," two things that make up our own personal perfumes.
》Taller women are more likely to have twins.
Some studies show that the level of insulin-like growth factor (IGF) is higher in taller women. This is a protein released by the liver that actually promotes growth in long bones' shafts. But at the same time, higher levels of IGF cause ovaries to be more sensitive, and as a result, more likely to ovulate.
》Researchers from the University of Utah made an interesting discovery that mothers of twins often live longer than other parents. They came to this conclusion after studying the birth records of over 59,000 women in the period of 1800-1970.
》One trick to distinguish identical twins is by looking at their belly buttons. These are essentially scars left in the place where the umbilical cord connected the baby to the mother, and they don't have anything to do with genetics.