Berkeley - The level of male hormones in the womb can influence an unborn child's future sexual orientation, according to new research from a University of California, Berkeley, professor who used an unusual technique measuring finger length - to gather evidence.
Marc Breedlove, professor of psychology, found that higher levels of these male hormones, or androgens, can create a greater than normal tendency for both males and females to develop a homosexual orientation.
"There is no gene that forces a person to be straight or gay," said Breedlove, who studies the biology of sexual orientation. "I believe there are many social and psychological, as well as biological, factors that make up sexual preference.
"Having said that, these data do suggest that there are some people in the world who are gay because of fetal androgen levels."
Breedlove's findings appear in this week's issue of the journal Nature.
Breedlove looked at relative finger length because it is influenced by androgen levels in the womb and thus is an approximate measure of fetal androgen levels.
In most people, the index finger is very slightly shorter than the ring finger, but, at least in the right hand, the difference is accentuated by higher levels of androgens during fetal development. Typically, in women, the two fingers of the right hand are nearly the same length. In men, the index finger is obviously shorter.
Breedlove collected data on 720 people who attended three San Francisco Bay Area street fairs in the fall of 1999. Using a portable copy machine, his research assistants had subjects lay their hands flat on the machine to record finger lengths. Breedlove also administered a questionnaire that explored birth order and sexual orientation.
According to the data collected, homosexual women, on average, had a more masculine finger length pattern - an index finger considerably shorter than the ring finger on the right hand - than did heterosexual women.
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Contact: Patricia McBroom
510-642-3734
University of California - Berkeley
28-Mar-2000