Nature vs Nurture: How your genes shape who you are

Summary

Dr. Nancy Siegel, a psychology professor at California State University Fullerton, shares insights from her research on twins. As a fraternal twin herself, she explores how genetics influence both physical and behavioral traits. Twin studies, particularly those involving twins raised apart, reveal the profound impact of genetic inheritance, even in unexpected areas like religious beliefs and political attitudes. While genetics play a significant role, Dr. Siegel emphasizes that they work probabilistically, not deterministically, meaning that the environment also plays a crucial part in shaping individual traits and behaviors.

Takeaways

• 😀 Dr. Nancy Siegel, a psychology professor, is a fraternal twin, and her personal experience with her twin sister sparked her interest in twin research.
• 😀 Twin studies help explore how genetics and environment influence behavior by comparing identical and fraternal twins.
• 😀 Identical twins share 100% of their genes, while fraternal twins share only 50%, making them useful for comparing genetic influences.
• 😀 Twin studies have revealed that genetics play a significant role in behaviors like intelligence, physical traits (height, weight), and mental abilities.
• 😀 Surprisingly, genetics also contribute to traits like religiosity, political attitudes, and social attitudes.
• 😀 Genes do not operate in deterministic ways. Instead, they work probabilistically, influencing outcomes based on environmental factors.
• 😀 Gene expression can differ even in identical twins, sometimes starting in the womb, leading to differences despite shared genetics.
• 😀 The similarities observed in identical twins raised apart are often more than expected, including unusual habits like nail-biting or headache descriptions.
• 😀 The challenge with these findings is that some people misunderstand how genes influence behavior, thinking they determine outcomes in a fixed way.
• 😀 While genes predispose certain traits, individuals can still change behaviors by altering their environment or taking actions to mitigate genetic predispositions.

Q & A

What motivated Dr. Nancy Siegel to pursue twin research?

Dr. Nancy Siegel was motivated to pursue twin research because she is a fraternal twin herself and was fascinated by the differences between her and her twin sister, despite having the same parents and environment.

How does Dr. Siegel explain the differences between her and her twin sister?

Dr. Siegel attributes the differences between her and her twin sister to genetics, explaining that while they shared the same environment and parents, they had different genetic predispositions.

What is the significance of including fraternal twins in twin studies?

Fraternal twins are included in twin studies as a natural control group to compare with identical twins. This helps to understand the influence of genetics by showing the differences in traits when identical twins, who share 100% of their genes, are compared to fraternal twins, who share 50%.

What is the primary difference between identical and fraternal twins in terms of genetics?

Identical twins share all of their genes, as they come from a single fertilized egg that splits, whereas fraternal twins share about 50% of their genes, as they are the result of two separate eggs fertilized by two sperm cells.

How do twin studies help scientists understand the role of genetics in behavior?

Twin studies provide valuable insights into the genetic and environmental influences on behavior by comparing identical twins, who share all their genes, with fraternal twins, who share only half their genes. If identical twins are more alike than fraternal twins, it suggests that genetics play a significant role.

What physical traits are known to have a strong genetic component according to Dr. Siegel?

Height and weight are two physical traits that have a substantial genetic component, as well as general intelligence, which has a slightly lesser but still significant genetic influence.

Which behaviors or characteristics have been shown to have a genetic component, according to recent research?

Recent research shows that behaviors and characteristics such as religiosity, political attitudes, and social attitudes also have a genetic component, in addition to more commonly studied traits like intelligence and physical features.

What is meant by genes working in 'probabilistic' ways rather than deterministic ways?

Genes work probabilistically, meaning they predispose individuals to certain traits or behaviors, but they do not determine them with certainty. Environmental factors and individual experiences can influence how and whether a gene is expressed.

How can environmental factors influence gene expression, even in identical twins?

Environmental factors can influence gene expression by activating or suppressing certain genes. Even though identical twins share the same DNA, differences in their environments, including prenatal conditions, can lead to different gene expressions and, therefore, different traits.

What are some of the unusual similarities found in identical twins raised apart?

Identical twins raised apart have shown surprising similarities, such as shared unusual habits, like scattering love letters to their wives, biting their nails down to the nub, or explaining the same mixed headache syndrome in identical ways. These similarities suggest that genetics, rather than random chance, plays a role in these behaviors.