It's not just humans who are gay or lesbian for even animals practice same-sex coupling, says a new research.
According to University of Oslo zoologist Petter Bockman, about 1,500 animal species are known to practice same-sex coupling, including bears, gorillas, flamingos, owls, salmon and many others.
If homosexuality is natural in the animal kingdom, then there is the question of why evolution hasn't eliminated this trait from the gene pool, since it doesn't lead to reproduction.
It may simply be for pleasure.
"Not every sexual act has a reproductive function," Live Science quoted Janet Mann, a biologist at Georgetown University who studies dolphins (homosexual behavior is very common in these marine mammals), as saying.
"That's true of humans and non-humans," Mann added.
Some scientists have proposed that being gay may serve its own evolutionary purpose.
"It could be a way that you strengthen bonds - that's one hypothesis. Another is that it could be practice for heterosexual sex. Bottlenose dolphin calves mount each other a lot. That might benefit them later on," Mann said.
Marlene Zuk, a biologist at the University of California, Riverside, suggested that gay individuals contribute to the gene pool of their community by nurturing their relatives' young without diverting resources by having their own offspring.
One thing that does seem to be exclusive to humans is homophobia.
"It's a very interesting question as to why anybody ever cares. There are different theories about why people find it threatening. Some think it disrupts male bonds, like you're not playing for the right team. The funny thing is that people say homosexuality is unnatural, that non-humans don't engage in homosexual behavior, but that's not true. Then they'll say it's base and animalistic," Mann said.