Scientists and people in general have wondered what determines people's sexual orientation and a recent study suggests that this preference could be determined by the income levels of their parents.
New research involving Swansea University (UK), the University of Vienna (Austria) and an American researcher examines the suggestion that parental economic status influences the sexual attraction that people experience later in life life.
Attraction to same-sex partners is common in humans, the study highlights, but the underlying biology and causes of homosexuality and bisexuality remain poorly understood.
Seeking to clarify the causes of different sexual orientations, Professor John Manning (Swansea University), Bernhard Fink (University of Vienna) and American evolutionary biologist and sociobiologist Robert Trivers conducted research that was recently published in Evolutionary Psychology.
According to the researchers, the highest frequencies of same-sex attraction were found in the children of the lowest income group (25 percent), the lowest frequencies in the slightly higher income group than others, and elevated frequencies of same-sex attraction in the children of the top 25 percent of the population.
The role of sex hormones
The research also found 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 authors have further speculated that high fetal estrogen is related to the roles of “female” and “submissive” in female and male homosexuals respectively. In addition, high prenatal testosterone may be related to “macho” and “assertive” roles in female and male homosexuals, respectively.
“These novel findings suggest that high fetal estrogen is a factor influencing same-sex attraction, both male and female, in children of low-income parents. Conversely, in male and female children of high-income parents, elevated fetal testosterone may be related to same-sex attraction,” stated Professor John Manning.
The research follows on from an earlier study involving Professor Manning and published last year, which found that low-income mothers feminize their children in utero by adjusting their hormones, while high-income mothers masculinize their children.
That study was based on the ratio between the lengths of a person's index and ring fingers, known as the 2D:4D ratio. A long ring finger is a marker of higher prenatal testosterone levels, and a long index finger is a marker of higher prenatal estrogen levels. Generally, compared to women, men have longer ring fingers, while compared to men, women have longer index fingers.