What identical twins separated at birth teach us about genetics - BBC REEL

Summary

Dr. Nancy Segal, a psychology professor at California State University, Fullerton, shares her journey into twin research, sparked by her experience as a fraternal twin. She explains how twin studies, particularly comparing identical and fraternal twins, provide insights into the influence of genetics and environment on behavior. Dr. Segal highlights surprising findings, such as genetic influences on intelligence, physical traits, and even political and religious attitudes. She emphasizes that genes work probabilistically, not deterministically, meaning environment plays a key role in gene expression, which can lead to differences even in identical twins.

Takeaways

• 🎓 Dr. Nancy Segal is a psychology professor at California State University, Fullerton, with a personal interest in twins stemming from being a fraternal twin herself.
• 🧬 Genetics plays a significant role in shaping who we are, as we all enter the world with unique predispositions.
• 👯‍♀️ Twin studies, especially those of twins raised apart, are crucial for understanding the influence of genetics and environment on behavior and traits.
• 🤝 Identical twins share all their genes, while fraternal twins share about half, similar to ordinary siblings, making the comparison between them valuable for genetic research.
• 🧠 Many behaviors, including physical traits like height and weight, general intelligence, and even social attitudes, have a substantial genetic component.
• 🧬 Genetics is not deterministic; it works probabilistically, predisposing individuals but not dictating their outcomes.
• 🌱 Gene expression can change based on environmental factors, and even identical twins can exhibit differences due to varying environmental triggers.
• 👶 Environmental influences on gene expression can start as early as in the womb, affecting the development of twins.
• 🌟 Identical twins raised apart show remarkable similarities, suggesting a strong genetic influence that interacts with their environments.
• 🤔 People who find genetic determinism challenging often misunderstand the probabilistic nature of genes and their interaction with the environment.
• 🌈 We have the capacity to change and alter our environments, which can lead to different behavioral expressions and potentially prevent or mitigate diseases.

Q & A

What initially sparked Dr. Nancy Segal's interest in twin research?

Dr. Nancy Segal's interest in twin research was sparked by her own experience as a fraternal twin and her fascination with the differences she had with her sister, despite having the same parents and environment.

How did Dr. Segal's understanding of genetics influence her view on the differences between her and her sister?

Studying psychology and learning about genetics at high school and graduate school helped Dr. Segal understand that people come into the world with their own predispositions, which explained the differences between her and her sister.

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

Fraternal twins are included as a natural control group in twin studies. They share half their genes on average, similar to ordinary siblings, which allows researchers to compare their resemblance to that of identical twins to determine the effect of genetics.

How do identical twins and fraternal twins differ genetically?

Identical twins share all their genes, having split from a single fertilized egg within the first two weeks after conception, while fraternal twins share half their genes on average, resulting from two separate eggs being fertilized by two different sperm.

What insights do twin studies provide into human behavior and genetics?

Twin studies provide insights into how genetic and environmental influences shape behavior. They reveal that many behaviors have a genetic component, and that genetics can explain a significant portion of the differences between individuals.

Which physical traits have been found to have substantial genetic components?

Height, weight, and brainwaves have been found to have substantial genetic components, with general intelligence also having a significant genetic component, though slightly less than the physical traits.

What surprising findings have emerged regarding genetic components in non-physical traits?

In the last 20 years, it has been surprising to find that traits such as religiosity, political attitudes, and social attitudes also have genetic components.

How do genes work in relation to behavior and environmental influences?

Genes do not work deterministically but probabilistically. They predispose individuals to certain behaviors, but the environment plays a crucial role in whether or not these genes are expressed.

Why is it significant that identical twins raised apart can show similarities in behavior and traits?

Identical twins raised apart share only their genes and not their environments. Any resemblance between them is tied to their common genes, which helps researchers understand the role of genetics in behavior and traits.

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

Some unusual similarities found include habits like scattering love letters around the house, nail-biting, and describing the same headache syndrome in an identical manner.

How does Dr. Segal respond to the challenge that the similarities in identical twins raised apart are due to random chance?

Dr. Segal believes that these similarities are not due to random chance, especially when they are rare. She suggests that they are tied to genes and how genes interact with environments.

What is Dr. Segal's view on the misconception that genes work in deterministic ways?

Dr. Segal clarifies that genes work in probabilistic ways, not deterministic ones. This means that while genes predispose individuals to certain behaviors, they do not set them in stone, and changes in environments can lead to different behavioral expressions.