LOS ANGELES, Oct 22, 2003 (United Press International via COMTEX) -- Differences in male and female brains are the result of genes -- not just hormones, a UCLA study indicates.

The study, published in this month's edition of Molecular Brain Research, refutes 30 years of scientific theory that solely credits hormones for brain development.

The UCLA discovery suggests sexual identity is hard-wired into the brain before birth and may offer physicians a tool for gender assignment of babies born with ambiguous genitalia.

"Our findings may help answer an important question -- why do we feel male or female?" said Dr. Eric Vilain, assistant professor of human genetics and urology at the David Geffen School of Medicine at UCLA.

"Sexual identity is rooted in every person's biology before birth and springs from a variation in our individual genome."

Researchers found 54 genes produced in different amounts in male and female mouse brains, prior to hormonal influence. Eighteen of the genes were produced at higher levels in male brains; 36 were produced at higher levels in female brains.

Copyright 2003 by United Press International.

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Last updated: 10/25/2003 - 10:42 AM