For some species, homosexuality 'an important driving force in evolution'

Here's the quote from New Scientist: "In a species where [same-sex sexual behavior] is common, it is an important driving force in evolution." You might think the opposite, that homosexuality would slow reproduction, and thus evolution. But that doesn't seem to be the case since it's so widespread in the natural world. How can homosexuality help drive evolution? For one, it could help strengthen social bonds, giving a species an advantage in the wild. Second, homosexual behavior may act as "practice for later sexual encounters with females."