Passage one
The similarities between identical twins often cause us to overlook their individualities. We tend to view them as two peas in a pod. However, no two people are absolutely the same. And even though identical twins might look and act similarly, they are, like any two people, two unique individuals.
Identical twins form when a single fertilized egg in the mothers body divides into two embryos. Since they come from the same genetic material, identical twins are the same sex and usually look alike. But, though their genes are similar, environmental factors---which are never the same in any two livesso shape the kind of people they will become.
These environmental factors provide identical twins with individual characteristics even before they are born. For example, blood flow and the infants positions inside the mothers womb give each twin a unique set of fingerprints. After birth, their surroundingsincluding the people they encounter and the experiences they have play a large role in molding their personalities.
Both genes and environment are significant in determining who we aretwins and non-twins alike. Surprisingly, studies have shown that identical twins who, for one reason or another, grow up apart have more personality similarities than those who grow up together. One reason for this may be that identical twins who grow up together feel the need to develop individual identities.
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