Birth Order
Recent studies found an increased chance of homosexuality in men whose mothers previously carried to term many male children. This effect is nullified if the man is left-handed.
Known as the ‘‘fraternal birth order’’ (FBO) effect, this theory has been backed up by strong evidence of its prenatal origin, although no evidence thus far has linked it to an exact prenatal mechanism. However, research suggests that this may be of immunological origin, caused by a maternal immune reaction against a substance crucial to male fetal development during pregnancy, which becomes increasingly likely after every male gestation. As a result of this immune effect, alterations in later-born males' prenatal development have been thought to occur. This process, known as the maternal immunization hypothesis (MIH), would begin when cells from a male fetus enter the mother's circulation during pregnancy or while giving birth. These Y-linked proteins would not be recognized in the mother's immune system due to the fact that she is female, causing her to develop antibodies which would travel through the placental barrier into the fetal compartment. From here, the anti-male bodies would then cross the blood/brain barrier (BBB) of the developing fetal brain, altering sex-dimorphic brain structures relative to sexual orientation, causing the exposed son to be more attracted to men over women.
Read more about this topic: Sexual Orientation, Measuring Sexual Orientation
Famous quotes containing the words birth and/or order:
“When we consider how much climate contributes to the happiness of our condition, by the fine sensation it excites, and the productions it is the parent of, we have reason to value highly the accident of birth in such a one as that of Virginia.”
—Thomas Jefferson (1743–1826)
“When we understand that man is the only animal who must create meaning, who must open a wedge into neutral nature, we already understand the essence of love. Love is the problem of an animal who must find life, create a dialogue with nature in order to experience his own being.”
—Ernest Becker (1924–1974)