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)
“To care for the quarrels of the past, to identify oneself passionately with a cause that became, politically speaking, a losing cause with the birth of the modern world, is to experience a kind of straining against reality, a rebellious nonconformity that, again, is rare in America, where children are instructed in the virtues of the system they live under, as though history had achieved a happy ending in American civics.”
—Mary McCarthy (1912–1989)
“In our science and philosophy, even, there is commonly no true and absolute account of things. The spirit of sect and bigotry has planted its hoof amid the stars. You have only to discuss the problem, whether the stars are inhabited or not, in order to discover it.”
—Henry David Thoreau (1817–1862)
“Other countries drink to get drunk, and this is accepted by everyone; in France, drunkenness is a consequence, never an intention. A drink is felt as the spinning out of a pleasure, not as the necessary cause of an effect which is sought: wine is not only a philtre, it is also the leisurely act of drinking.”
—Roland Barthes (1915–1980)