The burgeoning field of epigenetics could explain the biological roots of people being gay, say researchers. Epigenetics looks at how genes are expressed and the temporary markers that control this expression, known as “epi-marks.” In a study published online Tuesday, scientists working with the National Institute for Mathematical and Biological Synthesis (NIMBioS) explain how sex-specific epi-marks passed from father to daughter or mother to son could cause homosexuality.
Sergey Gavrilets, study co-author and associate director for scientific activities at the NIMBioS, said the transmission of sex-specific epi-marks between generations “is the most plausible evolutionary mechanism of the phenomenon of human homosexuality.”
In a press release, NIMBioS explains:
“While genes hold the instructions, epi-marks direct how those instructions are carried out – when, where and how much a gene is expressed during development. Epi-marks are usually produced anew each generation, but recent evidence demonstrates that they sometimes carry over between generations.”
This usually happens in response to spikes in testosterone — sex-specific epi-marks formed in early fetal development activate to protect the fetus from the testosterone surge. Otherwise, the high testosterone could cause female fetuses to ‘masculinze’ or vice versa for male fetuses.
Different epi-marks protect different sex traits from being masculinized or feminized, NIMBioS explains; some affect the genitals, others affect sexual identity and others affect sexual preference. But when epi-marks are transmitted from fathers to daughters or mothers to sons, “they may cause reversed effects, such as the feminization of some traits in sons, such as sexual preference, and similarly a partial masculinization of daughters.”