Identical twins may start out with the same genetic make-up but they drift apart genetically as the years pass, says an international team of researchers. Their study of identical twins show chemical changes after birth alter the way genes are expressed, a process known as epigenetics.
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.
Identical twins have the same set of epigenetic marks on the genome when they are born. But differences in the epigenome emerge as the twins grow older and become greater the longer they live apart, say a team of researchers led by Dr. Manel Esteller of the Spanish National Cancer Center in Madrid.
Differences in gene expression among older twin pairs were some four times greater than those observed in young twin pairs. There is widespread “epigenetic drift” associated with aging. The studies reported by Fraga et al.
These differences may widen as twins grow up. While infant identical twins can be almost indistinguishable, some can begin to look more unique as they age (though friends and family still confuse adult twins all the time, Segal says, as with the Colombian sets).
The research team found that identical twins who are reared apart had the same chance of being similar as twins who were raised together. Bouchard and his colleagues concluded that genetic factors have a large influence on behavioral habits demonstrating the influence of the genetics on development.
The longest interval between the birth of twins is 90 days, in the case of Molly and Benjamin West, dizygotic (fraternal) twins born in Baltimore, Maryland, USA to parents Lesa and David West (all USA) on 1 January and 30 March 1996.
There is no right or wrong answer, it's a personal preference. Some chose to be completely open or tell their twins to give a “smaller” twin leverage if he/she is older. Other choose not to tell so that they don't bicker about the subject or the dominate “older” twin doesn't have more leverage.
The average time between the birth of the first and second baby is generally about 17 minutes. 2 However, as long as the monitor shows the second baby is doing well there's no great need to speed things along.
Some say that twins are always hard (yet amazing), while others say they truly didn't find them to be difficult. A few said that the first two months with twins are easy (being in the rose-colored glasses phase), then reality hits from months 3-6 (when the sleep deprivation catches up), then it can get easier again.
Age. People over 30, and particularly those over age 35, are more likely to conceive twins. 4 This is because the level of follicle-stimulating hormone (FSH) rises as birthing parents get older. FSH is responsible for the development of eggs in the ovaries before they are released.
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 authors found that at nearly every age, identical twins survived longer than fraternal twins, who, in turn, had greater longevity than the general population. Why do twins live longer?
The authors of the study believe the reason twins live longer may be because of the social support they provide each other, and the psychological and health benefits that come with that social connection. "There is benefit to having someone who is socially close to you who is looking out for you," Sharrow said.
As identical twins get older they may look more and more different, because they are exposed to more diverse environments. The science of epigenetics explains how these environmental influences can affect the genes.
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.
So the firstborn is really the youngest. Answering the “which twin is older” question from strangers is one thing. Fielding the questions from friends, family, or the twins themselves is another story. You should discuss as a couple your approach for answering this question with people you know.
There is one particular power though which twins possess, longevity. Fraternal twins live longer than singletons and identical twins longer still. Male identical twins on average, saw the most benefit.
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.
This is supported by a Dutch study of adult twins, which found no significant difference in IQ between singletons and twins from the same families.
Very high-order multiple births
In 1997, the McCaughey septuplets, born in Des Moines, Iowa, became the first septuplets known to survive infancy. Multiple births of as many as eight babies have been born alive, the first surviving set on record goes to the Suleman octuplets, born in 2009 in Bellflower, California.
Multiples are generally born only a few minutes apart. If delivered by cesarian section, the interval between births is usually only a minute, maybe two. The interval is generally longer for vaginal deliveries, ranging from a few minutes to more than an hour.
While the typical definition of Irish twins is two children spaced 12 or fewer months apart, people do sometimes use the term more loosely to include children born 13, 14, or more months apart, particularly if the children end up in the same grade in school.