Blanchard has conducted research on factors that influence the development of sexual orientation, including biological factors. He has proposed a theory known as a fraternal birth order effect or "older brother effect". This theory is that the more older brothers a man has, the greater the probability is that he will have a homosexual sexual orientation. The number of older sisters has no effect, however. The same is not true for lesbians—neither the number of older brothers nor the number of older sisters appears to be related to the sexual orientation of women. The fraternal birth order effect is the strongest known predictor of sexual orientation, with each older brother increasing a man's odds of being gay by about 33%. Blanchard goes on to state that "A man's chance of being gay is pretty low to begin with --perhaps as low as 2%..." So having one older brother ups the chance to only about 2.6%."
Blanchard hypothesizes that the older brother effect is caused by interactions between a male fetus and the immune system of the mother: Because certain proteins (called H-y antigens) are produced by male and not by female fetuses, the mother's immune system reacts only to male fetuses and is more likely to produce a reaction with each successive exposure to a male fetus.
Read more about this topic: Ray Blanchard
Famous quotes containing the words fraternal, birth, order and/or effect:
“Between richer and poorer classes in a free country a mutually respecting antagonism is much healthier than pity on the one hand and dependence on the other, as is, perhaps, the next best thing to fraternal feeling.”
—Charles Horton Cooley (1864–1929)
“The unique and supreme voluptuousness of love lies in the certainty of committing evil. And men and women know from birth that in evil is found all sensual delight.”
—Charles Baudelaire (1821–1867)
“Our art is the finest, the noblest, the most suggestive, for it is the synthesis of all the arts. Sculpture, painting, literature, elocution, architecture, and music are its natural tools. But while it needs all of those artistic manifestations in order to be its whole self, it asks of its priest or priestess one indispensable virtue: “faith.””
—Sarah Bernhardt (1845–1923)
“We are such docile creatures, normally, that it takes a virus to jolt us out of life’s routine. A couple of days in a fever bed are, in a sense, health-giving; the change in body temperature, the change in pulse rate, and the change of scene have a restorative effect on the system equal to the hell they raise.”
—E.B. (Elwyn Brooks)