Researchers in Sweden and California believe they may have discovered a biological pre-disposition to sexuality through epigenetic causes.

Epigenetics is the study of epi-markers, markers on genes that control how that particular gene is expressed.

Usually the information on epi-markers is wiped clean from one generation to the next but now scientists believe gay people may retain the information from the parent of the opposite sex with lesbians inheriting the traits from their fathers and gay men gaining characteristics from their mothers.

The researchers report has been published in The Quarterly Review of Biology.