Final answer:
Fraternal twins, who share about 50% of their DNA and can be as different as any siblings, contrast with identical twins who share nearly 100% of their DNA. Studies have shown that environment and upbringing can result in differing characteristics and life choices in both fraternal and identical twins. The unique circumstances of twins provide insights into the nature vs. nurture debate in human development.
Step-by-step explanation:
When twins have no more in common than other siblings, they are typically fraternal twins, also known as dizygotic twins. This means they are two separate embryos that were fertilized by two different sperm cells, sharing 50% of their DNA, just like non-twin siblings. On the other hand, identical twins, or monozygotic twins, occur when a single zygote splits into two separate embryos, resulting in individuals who share nearly 100% of their DNA.
The Minnesota Study of Twins Reared Apart has found that identical twins, whether raised together or apart, have remarkably similar personalities. This points to the genetic basis of certain characteristics. However, fraternal twins, like the adoptive parent-child pairs mentioned, may have differences due to both genetic variability and distinct environmental factors influencing their development.
In the notable instance from 1968, where twin girls were part of a study, they were separated at birth and raised in different environments. Despite being twins, they might have developed different characteristics due to their unique upbringing, which shows the impact of environment on personal development, alongside genetic factors.
Examples of Differing Outcomes in Twins
- Adoptive siblings and similarly aged unrelated children raised together can still show differences despite shared environments.
- Identical twins may choose different career paths or lifestyles, illustrating the role of socialization.
- The special situation of twins represents a valuable resource for studying the influence of genetics and environment on human development.