New study shows ‘genetic underpinnings’ of bisexuality

(Los Angeles Blade graphic)

A new study conducted by University of Michigan researchers and published Jan. 3 in the journal Science Advances identifies genetic variations linked to human bisexual behavior and found that genetic characteristics associated with bisexuality are also linked to risk-taking behavior in males.

A statement released by the University of Michigan announcing the study says its findings may answer at least in part the longstanding question by evolutionary biologists of how the genes associated with same-sex behavior have persisted in humans because “same-sex sexual behavior does not result in offspring.”  

The study was conducted by University of Michigan Professor and evolutionary biologist Jianzhi Zhang and co-author and U.M. graduate student Siliang Song.

“The U.M. researchers analyzed data from more than 450,000 participants of European ancestry in the United Kingdom’s Biobank database of genetic and health information,” the university’s statement says. “Participants responded to a questionnaire that included the question, ‘Would you describe yourself as someone who takes risks?’”

According to the university statement, “The U.M. analysis revealed that male heterosexuals who carry the genetic variants associated with bisexual behavior, which are known as BSB-associated alleles, father more children than average. Furthermore, men who describe themselves as risk-takers tend to have more children and are more likely to carry BSB-associated alleles.”

Alleles are said to be matching genes, one from a person’s biological mother and the other from the biological father.

The statement says the two researchers also analyzed and compared the genetic makeup of both bisexual behavior and exclusive same-sex behavior, which they list as eSSB.

“When they compared the genetic basis of bisexual behavior to the genetic basis of eSSB, they found them to be significantly different,” the statement continues. “They found that eSSB-associated genetic variants are correlated with fewer children, which is expected to lead to a gradual decline in their frequency over time,” it says.

“However, the authors stress that their study looks at the genetic underpinnings of same-sex sexual behavior and not the behaviors themselves, which are affected by both genetic and environmental factors,” says the statement. It says the authors point out that the proportion of UK Biobank study participants reporting same-sex sexual behavior has risen in recent decades, mostly likely due to societal acceptance toward same-sex behavior.

In their study, the authors estimate a person’s bisexual behavior is influenced by genetics at about 40 percent and by environmental factors by about 60 percent.

“In addition, the authors say their new results ‘predominantly contribute to the diversity, richness, and better understanding of human sexuality. They are not in any way intended to suggest or endorse discrimination on the basis of sexual behavior,’ they wrote,” the University of Michigan statement says.

But an article about the study in Science Magazine says scientists and experts in the field of genetics have had mixed reactions to the study, with some questioning its reliance on the data from the UK Biobank surveys and others expressing concern that its claim that bisexuality is linked to risk-taking could perpetuate longstanding bias against bisexuals and gay men. 

The Science Magazine article reports that psychologist Michael Bailey of Northwestern University, who has studied factors that influence sexual orientation, believes the study is “based only on self-reported past sexual behavior of the UK Biobank participants, and not on other aspects of sexuality, such as sexual orientation or feelings.”

Other experts in the field of genetics and human behavior, however, believe the study sheds valuable light on the issue of bisexual and exclusive same-sex behavior.

The full study can be accessed at

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