Summary: A new study links same-sex attraction to parents’ socioeconomic status during pregnancy. Researchers report the highest frequency of same-sex attraction was found in children in the lowest income group and elevated levels of same-sex attraction in children who came from the most affluent backgrounds. They speculate higher levels of fetal estrogen are a factor in both male and female same-sex attraction in the lowest-income group, while elevated levels of fetal testosterone are a factor in the higher-income group. Higher fetal estrogen was related to more submissive roles in same-sex relationships, while higher fetal testosterone was associated with more assertive characteristics.
Source: Swansea University
Attraction to same-sex partners is common in humans but the biological influences on homosexuality and bisexuality are not fully understood.
Now new research involving Swansea University is examining the suggestion that sex hormones in the fetus influence the sexual attraction people experience later in life. Extending earlier work that linked parental income to fetal sex hormones Professor John Manning, of the Applied Sports, Technology, Exercise and Medicine (A-STEM) research team, and colleagues have, for the first time, considered links between parental income and sexual behavior of their adult children.
According to the researchers, the highest frequencies of same-sex attraction were found in the children of the lowest (25 percent) income group, the lowest frequencies in the income group slightly higher than others, and elevated frequencies of same-sex attraction in the children of the top 25 percent of the population.
The study, which has just been published in online journal Evolutionary Psychology, is a collaboration between Professor Manning, Bernhard Fink of the University of Vienna and the American evolutionary biologist and sociobiologist Robert Trivers.
Professor Manning said: “These novel findings suggest that high fetal estrogen is a factor in both male and female same-sex attraction in children of low-income parents. Conversely, in male and female children of high-income parents, high fetal testosterone may be linked to same-sex attraction. “
The authors have further speculated that high fetal estrogen is related to “femme” and “submissive” roles in female and male homosexuals respectively. Moreover, high prenatal testosterone may be linked to ‘butch’ and ‘assertive’ roles in female and male homosexuals respectively.”
The research follows on from a previous study involving Professor Manning published last year which found low-income mothers feminize their children in the womb by adjusting their hormones, whereas high-income mothers masculinize their children.
That study was based on the relationship between the length of a person’s index and ring fingers, known as the 2D:4D ratio. A long ring finger is a marker of higher levels of prenatal testosterone, and a long index finger is a marker of higher levels of prenatal estrogen. Generally, in comparison to women, men have longer ring fingers, whereas in comparison to men, women have longer index fingers.
About this neurodevelopment and sexual orientation research news
Parental Income and the Sexual Behavior of Their Adult Children: A Trivers–Willard Perspective
Parental income is negatively and linearly related to the digit ratio (2D:4D; a proxy for prenatal sex steroids) of their children.
Children of parents with high income are thought to be exposed to higher prenatal testosterone and develop lower 2D:4D. It is further hypothesized that 2D:4D relates to sexual orientation, although it is unclear whether the association is linear or curvilinear.
Here, we consider patterns of parental income and its association with the sexual behavior of their adult children in a large online study (the BBC internet study). There were curvilinear relationships with parental income in male and female children.
The highest frequencies of homosexuality and bisexuality were found in the lowest income group (bottom 25% of the population), the lowest frequencies in the income group representing the upper 50% of the population, and intermediate values in the other groups (low 50% and top 25% of the population).
Parental income showed a U-shaped association with scores for same-sex attraction and an inverted U-shaped association with opposite-sex attraction. Thus, for the first time, we show that same-sex attraction is related to parental income.
The curvilinear relationship between parental income and sexual behavior in their adult children may result from an association between very high fetal estrogen or testosterone and attraction to partners of the same sex.
Among non-heterosexuals, and in both sexes, very high fetal estrogen may be associated with femme or submissive sexual roles, and very high fetal testosterone with butch and assertive sexual roles.