Study Confirms Genes Don’t Determine Homosexuality

Sep 9, 2019

A study conducted by scientists from Harvard and MIT once again refutes the “born that way” reason for homosexuality. This massive study of nearly half a million people sought to determine if genetic factors contribute to same-sex sexual behavior.

The research was recently published in Science, a journal for the American Association for the Advancement of Science, and is the largest study ever conducted on this subject. While previous studies have not been as large, these prior studies have also concluded that there is no genetic cause of same-sex attraction. 

Andrea Ganna is lead author and European Molecular Biology Laboratory group leader at the Institute of Molecular Medicine in Finland and instructor at Massachusetts General and Harvard. Ganna led an international team of scientists who examined data from 477,522 people in the United States and the United Kingdom to see whether certain DNA genetic markers were linked to their sexual behavior.

Specifically, the researchers conducted a genome-wide association study (GWAS) on 408,995 individuals in the UK Biobank, a British health resource, and 68,527 Americans from the private genomics company 23andMe—all of whom remained anonymous and consented to the study which included their DNA data and responses to questions about sexual behaviors, sexual attraction and sexual identity. More than 26,000 participants reported at least one sexual encounter with someone of the same sex. Researchers in this study identified five specific genetic variants that were found to be “associated” with (not “the cause of”) same-sex behavior. Altogether they accounted for less than one percent of homosexual behavior.

“There is no gay gene that determines whether someone has same-sex partners,” said Ganna.

David Curtis, honorary professor at the UCL Genetics Institute at the University College London, said “This study clearly shows that there is no such thing as a ‘gay gene.’ There is no genetic variant in the population which has any substantial effect on sexual orientation.”

Ben Neale, an associate professor in the Analytic and Translational Genetics Unit at Massachusetts General Hospital, said, “There is no single gay gene, and a genetic test for if you're going to have a same-sex relationship is not going to work. It's effectively impossible to predict an individual's sexual behavior from their genome.”

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