Ganna and his colleagues also used the analysis to estimate that up to 25% of sexual behaviour can be explained by genetics, with the rest influenced by environmental and cultural factors - a figure similar to the findings of smaller studies. “There is no ‘gay gene’,” says lead study author Andrea Ganna, a geneticist at the Broad Institute of MIT and Harvard in Cambridge, Massachusetts. The findings, which are published on 29 August in Science and based on the genomes of nearly 500,000 people, shore up the results of earlier, smaller studies and confirm the suspicions of many scientists: while sexual preferences have a genetic component, no single gene has a large effect on sexual behaviours. The largest study 1 to date on the genetic basis of sexuality has revealed five spots on the human genome that are linked to same-sex sexual behaviour - but none of the markers are reliable enough to predict someone’s sexuality. Genetic variants associated with same-sex sexual behaviour can’t be used to predict someone’s sexual orientation.
