Two new studies and other analyses of the inheritance of sexual orientation in humans has indicated that same-sex sexual behavior has multiple genetic components but not a specific gene.
There might be thousands of genes influencing same-sex sexual behavior, each playing a small role, scientists believe. The new study found that all genetic effects likely account for about 32 percent of whether someone will have same-sex sex. Using a big-data technique called genome-wide association, the researchers estimated that common genetic variants — single-letter differences in DNA sequences — account for between 8 percent and 25 percent of same-sex sexual behavior. The rest of the 32 percent might involve genetic effects they could not measure, they said.”
The study analyzed 408,000 men and women from the U.K. Biobank between the ages of 40 and 69, and 70,000 customers of 23andMe with an average age of 51: “The researchers mainly focused on answers to one question: whether someone ever had sex with a same-sex partner, even once.”
Andrea Ganna, lead author and European Molecular Biology Laboratory group leader at the Institute of Molecular Medicine in Finland, said the research reinforces the understanding that same-sex sexual behavior is simply “a natural part of our diversity as a species.” The new study, published Thursday in the journal Science, is not the first to explore the link between genetics and same-sex behavior, but it is the largest of its kind, and experts say it provides one of the clearest pictures of genes and sexuality.