The international research team, which includes scientists from Sweden, Denmark, the UK, and the U.S., looked at genetic data collected from earlier studies and projects, including from the consumer DNA testing company 23andMe. In total, just over 470,000 people were included.

The researchers performed a type of analysis known as a genome-wide association study. These studies sweep through the genomes of people and look for any variations in genes--also called markers--that could be linked to whatever other variables they're testing for. In this study, that variable was whether a person had reported ever having sex with someone of the same sex.

"This study is the largest and most thorough investigation into the genetics of same sex sexual behavior to date," said study author Ben Neale, director of genetics in the Stanley Center for Psychiatric Research at the Broad Institute of MIT and Harvard University, in a press conference on Tuesday.

All told, there were five markers that were "significantly" associated with same-sex behavior. That means that these genetic markers were found often enough in people with a history of same-sex behavior that they could be a relevant contributor. But if even someone had all these markers at birth, the authors estimated, they would be less than 1 percent more likely to someday report same-sex behavior than someone born without them.