Twins have always fascinated mankind, inspiring legends, beliefs and stereotypes that vary from culture to culture. Their special bond has given rise to a multitude of clichés, some of them erroneous, that influence the way they are perceived in society.
Monozygotes vs. dizygotes: understanding the difference
There are 2 types of twins:
Monozygotic twins (or identical twins) result from the division of a single egg fertilised by a single sperm. They therefore share 100% of their genetic material, making them genetically identical. Their physical resemblance and character are often similar, although this is not always the case. They are of the same sex and have the same blood group. The only difference between them is their fingerprints, which are distinct.
Dizygotic twins (or fraternal twins) result from the fertilisation of two separate eggs by two different sperm cells. Generally speaking, these twins are no more alike than siblings born at different times. They share about 50% of their genetic material, as do all other siblings. They may be of the same sex, or of different sexes.
The stereotypes associated with monozygotic and dizygotic twins are often influenced by their rarity.
Clichés: Telepathy, Genetics and Conception
1. Telepathy: myth or reality?
One of the most common stereotypes about twins is the idea that they possess telepathic powers. According to this popular belief, twins are able to understand each other without the need for words, to feel what the other is feeling, or even to predict the other’s actions from a distance. In reality, no scientific study has proven the existence of telepathy, and these phenomena can often be explained by very close ties and an increased ability to read each other’s social signals. Twins can be particularly synchronised because of their shared experiences, which can give the illusion of extra-sensory communication.Foods and factors favouring the conception of twins
2. Genetics: Twins and destiny
The idea that twins, particularly monozygotic twins, share not only physical traits but also similar behaviours and personalities, fuels another stereotype. Although genetics play an essential role in the development of twins, the reality is far more complex. Genetics can influence traits such as eye colour or the risk of certain diseases, but environment, upbringing and even personal choices have a significant influence on personality. For example, two monozygotic twins may share similar physical traits but develop completely different interests or preferences as a result of external factors.
When it comes to conceiving twins, there are genetic factors that influence the likelihood of having dizygotic twins. If dizygotic twins occur frequently in a woman’s family, particularly on her mother’s side, this can increase the chances of conceiving them. Monozygotic twins, on the other hand, occur completely at random, and there is no particular genetic factor that favours their appearance. So the presence of twins in the family does not increase the chances of having monozygotic twins, but it can have an impact on dizygotic twins.
3. Foods and factors favouring the conception of twins
Another widespread cliché is the idea that certain foods or behaviours favour the conception of twins. Although genetics play a crucial role, some studies suggest that certain foods can actually influence the chances of having twins, particularly dizygotic twins.
In Africa, for example, there is a popular belief that eating plenty of sweet potatoes can increase the chances of having twins. Sweet potatoes are rich in a compound called insulin-like growth factor (IGF), which is a hormone with properties similar to those of oestrogen. This hormone stimulates cell growth and could encourage the release of several eggs during ovulation, thereby increasing the chances of conceiving dizygotic twins. In some African countries, notably Nigeria, around 1 in 22 births are twins, a much higher rate than in other parts of the world.
However, it is important to note that, although certain foods such as sweet potatoes have been associated with an increase in twin births in certain regions, these results are still being studied, and other factors, such as the mother’s age (women over 30 are more likely to conceive dizygotic twins), family history or fertility treatments, play a much more decisive role in the conception of twins. Diet, although potentially influential, does not conclusively guarantee the birth of twins.
Twins are therefore often at the heart of fascinating popular beliefs. Whether it’s the idea of telepathy, absolute genetic similarities, or diets that favour their conception, these stereotypes are firmly rooted in the collective imagination. Yet the scientific reality behind twins is far more complex and nuanced, involving both genetic and environmental factors. What remains constant, however, is the wonder of these unique relationships, even if they are not nearly as mystical as some stereotypes would have us believe.
