“Current evidence indicates that sexual differentiation of the human brain occurs during fetal and neonatal development and programs our gender identity—our feeling of being male or female and our sexual orientation as hetero-, homo-, or bisexual.”

“This sexual differentiation process is accompanied by many structural and functional brain differences among these groups.”

“The excellent imaging research of Ivanka Savic’s group in past years has provided strong evidence for structural and functional brain differences related to gender and sexual orientation. The study of these differences has emerged from an era of prejudice and fear such as I experienced 20 years ago.”

“Neurobiological research related to sexual orientation in humans is only just gathering momentum, but the evidence already shows that humans have a vast array of brain differences, not only in relation to gender, but also in relation to sexual orientation.”

D.F. Swaab
Proceedings Of The National Academy Of Sciences
Volume 105 #30 — 2008 — page 10273
“….brain research has revealed structural differences in the hypothalamus in relation to biological sex and sexual orientation.”
“Differences in size and cell number of various nuclei in the hypothalamus for homosexual versus heterosexual men have recently been reported in two studies. We have found that a cluster of cells in the preoptic area of the human hypothalamus contains about twice as many cells in young adult men as in women.”

“We have called this cluster the sexually dimorphic nucleus.”

“Sexual differentiation to the human brain takes place much later than originally claimed. At birth the sexually dimorphic nucleus contains only some 20% of the cells found at 2 to 4 years of age. The cell number rapidly increases in boys and girls at the same rate until 2 to 4 years of age. After that age period, a decrease in cell number takes place in girls, but not in boys. This causes the sexual differentiation of the sexually dimorphic nucleus.”

This postnatal period of hypothalamic differentiation indicates that, in addition to genetic factors, a multitude of environmental and psychosocial factors may have profound influence on the sexual differentiation of the brain.”

“…..in a sample of brains of homosexual men we did find that an area of the hypothalamus called the suprachiasmatic nucleus contains twice as many cells as the sexually dimorphic nucleus of a heterosexual group.”

A recent report by LeVay claims that another nucleus, INAH-3, is more than twice as large in heterosexual as in homosexual men, whereas Allen and Gorski found that the anterior commissure was larger in homosexual men than in heterosexual men or women.”

D.F. Swaab, L.J.Gooren, M.A.Hofman
Brain Research, gender and sexual orientation
Journal Of Homosexuality — Volume 28 #3 & 4 — 1995 — page 283


ETG info: major social issues —– http://theetgtrackclub.com/documents/TheETGSocialIssues.pdf