In a peer-reviewed study published in Science, researchers found evidence that many genetic variants contribute to same-sex sexual behavior, but each has a small influence. When taken together, the variants explain only a minority of a person’s likelihood of ever engaging in sexual behavior with a person of the same sex.

The study concludes that both genetics and non-genetic factors play important roles.

Five locations in the human genome were associated with this trait at a statistically significant level, but these five loci capture only a tiny fraction of the genome's overall contribution (far less than one percent). The analysis further revealed that thousands of other variants also make tiny contributions that, together with the five loci, account for between 8 and 25 percent of the variation in self-reported same-sex sexual behavior. Much of the remainder is likely due to non-genetic factors.

These results do not make any conclusive statements about the degree to which “nature” and “nurture” influence sexual orientation or behavior, but indicate that both are likely to play a role.

These genetic results — likely thousands of variants, each with a very small effect — are similar to those for many other complex traits, like height, and indicate that same-sex sexual behavior is a normal part of human variation.

According to the study, there is no “gay gene” that determines whether a person will have same-sex partners in their lifetime. The findings indicate that it is impossible to meaningfully predict an individual’s same-sex sexual behavior from genetics.

PERSPECTIVES

The authors — and the Broad Institute of MIT and Harvard — note that the research raises important social, ethical, and scientific issues that are worth considering and discussing.

This study represents the work of a group of scientists, including faculty and students, who were interested in this topic. Scientists are independent and free to consider research questions, provided they have appropriate approvals to use the data. Here, the researchers received permission from UK Biobank and 23andMe to analyze these datasets, and individuals included in these datasets provided consent for their information to be used for approved research purposes. 23andMe participants also gave a “secondary consent” specifically for studies involving genetics and sexual activity. The paper was subject to rigorous peer-review and was published in a world-leading scientific journal.

The study’s authors — some who identify as heterosexual, and some who identify as gay — engaged a number of experts in LGBTQIA+ advocacy and research organizations in the US and around the world as they prepared the study and the publication. These experts offered important feedback, including concerning the language used in the paper and related materials, to help ensure that the study was done rigorously and the findings were clearly and responsibly communicated.

At the Broad Institute, several members of the Out@Broad group, which includes members of the LGBTQIA+ community and their allies, worked with some of the study authors to raise concerns about the project itself — including whether the authors should have undertaken the research. They also made suggestions around language and scientific figures, and flagged possible misinterpretations of the findings.

Because we believe it is important to represent a range of perspectives about this work, we invited members of the Broad community and others to provide their thoughts on the study, the process, the implications, and lessons we might learn.

Here are their perspectives, which we hope will inform a needed discussion