Twins share the same genes but their environments become more different as they age. This unique aspect of twins makes them an excellent model for understanding how genes and the environment contribute to certain traits, especially complex behaviors and diseases.
To form identical or monozygotic twins, one fertilised egg (ovum) splits and develops into two babies with exactly the same genetic information. To form fraternal or dizygotic twins, two eggs (ova) are fertilised by two sperm and produce two genetically unique children.
They have a special bond like no other.
They seem to understand every word. Sometimes even just a touch or a simple gesture can calm the other's fears. Their dynamic is unique and only between the two of them. And they always have someone to play with, which gives you a little more “me time” as they get older.
What are the benefits for the twins? Their buddy is always there. They've known each other since they can remember and that is very comforting. They are also a little more social than the average child since they are used to being with another kid since the beginning.
Twins can occur either when two separate eggs become fertilized in the womb or when a single fertilized egg splits into two embryos. Having twins is more common now than it was in the past. According to the Centers for Disease Control and Prevention (CDC) , twin births have nearly doubled over the last 40 years.
The hardest thing about having twins is...
“Managing the movement of two babies. Carrying them both up and down the stairs, getting them into the car, etc.” —Simeon R. “Often having to make one baby wait!” —Catharine D. “Being outnumbered—the logistics of two on one is definitely the hardest.
The results suggest that twin fetuses are aware of their counterparts in the womb, that they prefer to interact with them, and that they respond to them in special ways. Contact between them appeared to be planned—not an accidental outcome of spatial proximity, says study co-author Cristina Becchio of Turin.
The findings show that twins have a survival advantage over the general population at nearly every age, and between the two types of twins, identical twins have a survival advantage over fraternal twins, said David Sharrow, the lead author of the study and a demographer and postdoctoral researcher at the University of ...
Being a twin has its benefits—tricking people, having a lifelong companion, sharing clothes—but it also has downsides. Many twins struggle to cultivate their own identities, while being so similar to one another. And that struggle lasts a lifetime, according to a recent study.
The bond between twins is unlike any other sibling connection. It's powerful and unique; only 3.3 percent of births are twins, according to data from the CDC.
There are twins who say they have felt each other's pain. And their close relationship and nearly-identical physical structure means there could be a sliver of truth in the theory — as pain can be psychological and can be felt empathetically.
Identical twins may say that they are not attracted to the same people. However, researcher Nancy Segal surmises that twins actually feel the same attractions, but as soon as one twin makes her interest known, the second twin will not pursue the other's object of interest.
Monoamniotic-monochorionic Twins
This is the rarest type of twin, and it means a riskier pregnancy as the babies can get tangled in their own umbilical cords. If you have monoamniotic-monochorionic twins, your healthcare provider will monitor your pregnancy closely.
Identical twins reported similar levels of happiness, while fraternal twins exhibited greater variation in their reported sense of well-being. These results were found in families of twins raised together and extended with twins reared apart.
"Twins tend to be closer than typical siblings — they share a bond that is oftentimes unexplainable," Maureen Healy, an expert on sensitive children and author of Growing Happy Kids, tells Romper. "Many believe this is rooted in genetics, such as identical twins sharing the same DNA."
The Science of Fraternal Twins. Mixed-gender twins are the most common type of fraternals, some 50 percent are boy-girl. To understand this combination: Males have XY chromosomes, females have XX chromosomes. You have a girl twin when the father's X chromosome combines with the mother's X chromosome.
Identical twins are almost always the same sex, although there are some rare exceptions to this rule. Because identical twins occur when a single fertilized egg splits and forms two embryos, each embryo has the same chromosomes (usually, XX for girls or XY for boys).
Identical twins do not have identical fingerprints, even though their identical genes give them very similar patterns. 1 The fetus begins developing fingerprint patterns in the early weeks of pregnancy. Small differences in the womb environment conspire to give each twin different, but similar, fingerprints.
Fraternal twins live longer than singletons and identical twins longer still. Male identical twins on average, saw the most benefit. The rarity of twins has inspired many myths about them.
Both results were statistically significant. Moms of twins also were older at the time of their last birth. The age at last birth averaged 39.7 years for women born before 1870, and 36.2 years for women born during 1870-1899. Moms of twins had their last births 4.8 months later and 14 months later, respectively.
When analyzing the data by gender, the researchers found that female identical twins lived, on average, about 63.4 years, whereas female fraternal twins lived about 61.4 years and the general Danish female population lived about 58.8 years, Sharrow said.
You might have heard that twins “run in families”. And that can be true! Compared with the general population, women with a mother or sister who have had twins are twice as likely to have twins themselves. Birth of twins has significantly increased over the past years, as you can see on the graph below.
However, for a given pregnancy, only the mother's genetics matter. Fraternal twins happen when two eggs are simultaneously fertilized instead of just one. A father's genes can't make a woman release two eggs.