First-borns are typically smarter, while younger siblings get better grades and are more outgoing, the researchers say.
If two twins in an identical pair tend to have closer IQ's than two twins in a fraternal pair, then genes probably play a role in IQ. And that is just what we see. Identical twins are definitely more likely to share the same IQ than are fraternal twins. So genes do play a role in IQ.
It is shown that weight and birth order can affect not only personality and the way in which twins interact with each other, but can also affect family interaction. Particular attention has been given to the effect on and of the preceding sibling.
Classically, the bigger twin is the more physically dominant. It's basic human nature, and particularly applicable to boys as they hit puberty. It happens often with singleton siblings too… the older is bigger and enforces him/herself through physical dominance.
Most often, fetuses known in utero as twin A are also first born and thus retain their label. However, this is not always the case, such that the twin A newborn was previously labeled twin B in utero and vice versa.
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.
And because the death rate in the womb is higher for twins than for singleton births, female twins are more common than male twins.
D. graduate in anthropology at the University of Utah. Smith adds: "The prevailing view is that the burden of childbearing on women is heavier when bearing twins. But we found the opposite: women who naturally bear twins in fact live longer and are actually more fertile."
This is why fraternal twins run in families. However, only women ovulate. So, the mother's genes control this and the fathers don't. This is why having a background of twins in the family matters only if it is on the mother's side.
As a parent of twins, I'm pretty sure that you know the answer to the question “which twin is older?” It is, of course, the child that was born first.
For vaginal delivery of both infants, the twins decide birth order by their placement in the uterus. Once the babies are large enough to stay in one position in the womb, the twin lowest in the uterus is known as Baby A and the one furthest from there is Baby B, according to the Stanford Medicine News Center.
“Having twins is not twice as hard—it's exponentially more difficult,” says Natalie Diaz, author of What To Do When You're Having Two and CEO of Twiniversity, a global support network for parents of twins.
It was concluded, among many other things, that identical twins are about 85 percent similar for IQ, whereas fraternal twins are about 60 percent similar. This would seem to indicate that half of the variation in intelligence is due to genes.
We all think our babies are the cleverest, but IQ isn't everything. The sorts of abilities needed to do well in IQ tests (verbal and spatial working memory, attention tasks, verbal knowledge and motor speed ability) are certainly inheritable, as many studies involving identical and fraternal twins have shown.
Like most aspects of human behavior and cognition, intelligence is a complex trait that is influenced by both genetic and environmental factors.
In ancient times, the Yoruba viewed twins with suspicion, and sometimes sacrificed them. But now twins are considered lucky. In contrast to the Western view, the firstborn twin is considered the younger of the two. The Yoruba believe that the "senior" twin sent the younger one out first to scout the world.
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.
Longer lives
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.
Factors that increase the chance of twins include: consuming high amounts of dairy foods, being over the age of 30, and conceiving while breastfeeding. Many fertility drugs including Clomid, Gonal-F, and Follistim also increase the odds of a twin pregnancy.
Yes, some types of twins are hereditary, meaning that twins run in families. Heredity on the mother's side ups a couple's odds of conceiving fraternal twins. Fraternal twins are two babies from two different eggs that were released from the ovaries simultaneously.
How your babies lie in the womb. The most common way for twins to lie is both with their heads down - the best for birth. There's not a lot of room in your womb, so it's quite common for one or both babies to be feet or bottom down (breech).