Chicago, Aug. 30 -- The largest study of its kind found new evidence that genes contribute to same-sex sexual behavior, but it echoes research that says there are no specific genes that make people gay.

The genome-wide research on DNA from nearly half a million U.S. and U.K. adults identified five genetic variants not previously linked with gay or lesbian sexuality. The variants were more common in people who reported ever having had a same-sex sexual partner. That includes people whose partners were exclusively of the same sex and those who mostly reported heterosexual behavior.

The researchers said thousands more genetic variants likely are involved and interact with factors that aren't inherited, but that none of them cause the behav...