As mounting research strives to understand how much of who we are is controlled by our genes, research out of UCLA offers even more understanding of what genes can do. New findings suggest there are 54 genes that explain the different organization between male and female brains.
Researchers offer evidence in their report that sexual identity is hard-wired and is determined before a person is even born. These findings negate long-held beliefs that testosterone and estrogen were responsible for sexually organizing the brain. It was thought that more testosterone production was all it took for a person to be "male."
In this study, researchers performed two different genetic tests comparing the production of genes in male and female mice brains before the animal developed sex organs. They discovered 54 genes that were produced in different amounts in male and female brains -- independent of hormonal influences. Of those 54 genes, 18 were produced in higher quantities in the male brain and 36 were found in higher quantities in the female brain.
Researchers say they didn't expect to find genetic differences between the sexes' brains, but they discovered that the male and female brains differed in many measurable ways, including anatomy and function.
Researchers hope these findings will help doctors assign a gender to the 1 percent of all children who are born with malformed genitalia. These individuals account for about 3 million births each year. In one in 3,000 births, the malformation is so severe that doctors cannot even tell parents whether they had a boy or a girl. Doctors say this may also help explain the origin of homosexuality in the future.