Scientists may have finally solved the puzzle of what makes a person gay, and how it is passed from parents to their children.

A group of scientists suggested Tuesday that homosexuals get that trait from their opposite-sex parents: A lesbian will almost always get the trait from her father, while a gay man will get the trait from his mother.

The hereditary link of homosexuality has long been established, but scientists knew it was not a strictly genetic link, because there are many pairs of identical twins who have differing sexualities. Scientists from the National Institute for Mathematical and Biological Synthesis say homosexuality seems to have an epigenetic, not a genetic link.

Long thought to have some sort of hereditary link, a group of scientists suggested Tuesday that homosexuality is linked to epi-marks — extra layers of information that control how certain genes are expressed. These epi-marks are usually, but not always, "erased" between generations. In homosexuals, these epi-marks aren't erased — they're passed from father-to-daughter or mother-to-son, explains William Rice, an evolutionary biologist at the University of California Santa Barbara and lead author of the study.

-more at US News

also:

[ Watch the Video: Researchers Say They Have Found Genetic Switches for Homosexuality ]

Related articles

• Group of Scientists Believe They Have Unlocked Hereditary Question of Why People are Gay (towleroad.com)
• Your Mother Made You Gay (joemygod.blogspot.com)

"Unnatural" Nature, Immoral Butterflies: The Great Cover-Up of Animal Homosexuality

Back in 2000, an eminent and otherwise respectable biologist declared that except for a few instances observed among primates, there was no evidence of homosexuality among animals:

When animals have access to the opposite sex, homosexuality is virtually unknown in nature, with some rare exceptions among primates."

-G. Barlow, 2000

This was breathtakingly inaccurate. Just the previous year another biologist, Bruce Bagemihl,had published a book summarizing previously published scientific papers which described homosexual behaviour in over 300 species of animals and birds (listing dozens of papers for each), and also listing additional species of reptiles, amphibians, fish and even insects - over a thousand species in all, and tens of thousands of peer-reviewed articles. The first recorded observations of animal homosexuality were two millenia ago, by the ancient Greeks. In modern times, the first formal publication of scientific observations go back over 150 years. Photographic evidence of male swan couples has existed since the mid-nineteenth century.

Even this illustration, of male beetles doing it, was published as long ago as 1896:

Male Scarab Beetles, 1896