What Twins Separated At Birth Teach Us About Human Genetics - Nancy Segal | Modern Wisdom 667

Added: Aug 16, 2023

Segal begins by explaining the kinship genetic theory proposed by William Hamilton, which suggests that individuals feel greater cooperation, altruism, and investment in people with whom they share a higher degree of genetic relatedness. Her research has shown that identical twins, who share all their genes, are more cooperative and socially closer than fraternal twins, who share only 50% of their genes on average. This finding supports the idea that genetic relatedness plays a role in social behavior. Segal also explores the emotional connection between identical twins, which she believes is closer than any other relationship, including that between mothers and children. Her study on the loss of a twin found that identical twins grieved more for their co-twin than for any other relative, further supporting the influence of genetic relatedness on emotional bonds. The discussion then shifts to twins and sports, with Segal highlighting the remarkable level of similarity in athletic abilities among identical twins. She suggests that their shared genes and motivations contribute to their success. Additionally, a victory for one twin is often seen as a victory for both, indicating a high level of selflessness and cooperation. Segal explains that twins recognize their similarity not only based on physical appearance but also through shared mannerisms, interests, and temperaments. Her study on twins raised apart found that even those who recently met developed close relationships quickly due to these perceived similarities. One of the most fascinating cases discussed by Segal involves a same-sex couple who had twins through a surrogate. The twins were conceived using the sperm of both fathers, resulting in what Segal refers to as "half-half twins." This case sparked a legal battle when the U.S. State Department refused to issue passports to both children, threatening to separate the family. The case eventually settled in favor of the family, leading to changes in the Foreign Affairs manual to prevent similar situations in the future. The conversation then shifts to the Western Mark effect, which refers to the phenomenon where identical twins who are both gay rarely become each other's partners. Segal shares that she has observed this pattern in her research, particularly in cases of identical twins raised together. However, she also mentions a case of identical twin men raised apart who became each other's lovers when they met, suggesting that the Western Mark effect may not apply in all situations. Segal also discusses the concept of genetic sexual attraction, which refers to the intense attraction that can develop between relatives who reunite after being separated at birth or during early childhood. She explains that this phenomenon has been observed in cases of mothers and sons, fathers and daughters, and even male-female twins who were separated at birth. The podcast explores the legal and ethical implications of accidental incest, with Segal mentioning that in some cases, twins who are in a relationship have been allowed to marry without being forced to separate. She suggests that there may be a small cohort of twins raised apart who are exempt from societal norms due to their unique circumstances. Segal shares some of the most remarkable similarities she has observed in twins who were raised apart, highlighting the specificity of these similarities. She also discusses the relationship between genetics and various psychopathologies, such as schizophrenia, bipolar disorder, autism, and dementia. Her research has found a higher occurrence of these conditions in identical twins compared to fraternal twins, indicating a genetic component. The podcast continues with Segal discussing the genetic influence on body mass index (BMI) and weight. She explains that there is a genetic component to BMI and weight, with identical twins showing a higher similarity than fraternal twins. However, she notes that the influence of genetics differs between males and females. The discussion also touches on the impact of the internet on tracking family history and reuniting twins. Dr. Segal mentions the case of twins who found each other through online videos and the growing interest in genealogy and ancestry. She regrets not asking her own grandfather more questions about his immigration from Russia and emphasizes the value of understanding one's family history. Dr. Segal then explores the concept of identical twins and the fascination they evoke in people. She explains that the expectation of individual differences in behavior and appearance makes identical twins particularly intriguing. She also mentions the existence of websites that help people find others who look like them or resemble their artwork. The conversation shifts to the criticisms faced by twin studies, particularly regarding methodology and conclusions. Dr. Segal acknowledges these concerns but argues that critics often lack the necessary experience and expertise to make informed judgments. She highlights the robustness of twin study findings, which have been replicated across different populations and protocols. Dr. Segal discusses her involvement in the Minnesota Study of Twins Reared Apart, a groundbreaking research project that examined the similarities and differences between identical and fraternal twins raised in different environments. She mentions the large sample size of the study and the valuable insights gained from studying twins in a laboratory setting. The podcast also explores the topic of biracial twins and the unique challenges they face. Dr. Segal shares her research on the different life experiences of biracial twins and the parenting challenges involved. She wonders if parents feel a greater kinship with the child who looks more like them racially and ponders the possibility of less paternity uncertainty in biracial couples. The conversation concludes with a discussion on the use of film in twin studies. Dr. Segal emphasizes the value of observing twins in a naturalistic setting and the insights that can be gained from visual media. She recommends several films, including "Tell Me Who I Am" and "The Twinning Reaction," which explore the complexities of twin relationships and identity.