A recent study investigated the theory that the levels of sex hormones present in the fetus may play a role in shaping an individual’s sexual attraction later in life.
The attraction to same-sex partners is prevalent in humans, but the underlying biology and causes of homosexuality and bisexuality remain not fully understood.
A new study involving a researcher from Swansea University is exploring the possibility that sex hormones present in the fetus may play a role in shaping an individual’s sexual attraction later in life. Building on previous research linking parental income to fetal sex hormones, the study, for the first time, examines the potential connection between parental income and the sexual behavior of 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 recently been published in 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.
Reference: “Parental Income and the Sexual Behavior of Their Adult Children: A Trivers–Willard Perspective” by John T. Manning, Bernhard Fink and Robert Trivers, 12 December 2022, Evolutionary Psychology.