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he Strange Origin of Twins: Why Does the Same "I" Appear Twice?
Twins are two offspring produced from the same pregnancy. They can be monozygotic (identical), meaning they come from the same fertilized egg that splits to form two embryos, or dizygotic (non-identical), meaning each twin develops from a different egg and has its own child. of sperm for fertilization. Since monozygotic twins come from the same fertilized egg, they share the same sex, whereas dizygotic twins can have the same or different sexes. In rare cases, dizygotic twins can even have the same mother and different fathers, which is called a heteropaternal pregnancy. In contrast, a single fetus developing alone in the uterus is called a singleton pregnancy.
The rate of twin births increased by 76 per cent between 1980 and 2009, sparking debate about why.
According to statistics, the twin birth rate in the United States increased from 9.4 to 16.7 pairs per 1,000 births between 1980 and 2009, showing that twin births are becoming more and more common. On the other hand, the Yoruba people in Nigeria have been found to have the highest twin birth rate in the world, at 45-50 pairs per 1,000 births, which is related to their specific dietary habits.
Many factors can increase your chances of having twins, from the mother's age to fertility treatments. Studies have shown that a family history of twins increases a woman's chances of having twins.
Types of twins
In humans, dizygotic twins are more common than monozygotic twins. Most twins are either dizygotic or monozygotic, and the processes by which they form differ. Dizygotic twins usually occur when two eggs are fertilized at the same time, while monozygotic twins occur when the same egg splits into two embryos.
Whether they are dizygotic twins or monozygotic twins, their genetic combination and developmental process are hot topics for scientists to study.
The study found that although the genomes of monozygotic twins are almost identical, their personalities, IQs, etc. may differ due to differences in environmental factors and gene expression.
Mechanism of twin formation
The formation of monozygotic twins is relatively rare, occurring only 3 to 4 times per 1,000 births. As for the specific mechanism of its formation, some studies have shown that monozygotic twins may be caused by the failure of the embryo to completely separate at the beginning of formation after fertilization. The details of this process are still not fully understood.
The mother's environment and genetic factors can affect the formation of twins to varying degrees.
Genetic similarities between twins
Although identical twins have nearly identical genomes, environmental changes experienced during their lifetimes can affect gene expression, resulting in different phenotypes. This is why even identical twins with almost identical genes can have different personalities and appearances.
The social and cultural significance of twins
In some cultures, twins are viewed as special and sometimes even mysterious beings. Residents in some places specifically encourage the birth of twins and believe that it is a sign of luck.
The existence of twins not only challenges our understanding of individual identity, but also triggers a lot of philosophical thinking about the relationship between self and others. In this case, what role will the other person with the same "I" play in society?
Whether you are a parent of twins or one of the twins, this phenomenon is enough to trigger fundamental thinking about human existence: if we can live in the same space with another "me", does it mean that we are Does our understanding of self-awareness need to be redefined?
Can this discussion of identity extend to deeper philosophical questions rather than just the duplication of genes?
