Discuss what is known about the "older brother effect" on sexual orientation

Question

What will be an ideal response?

Answer 1

- Researchers have also discovered a new, possible biological basis of sexual orientation that has become known as the "older brother effect." A statistically significant association has been found demonstrating that as the number of older biological brothers a man has increases, so do his chances of being gay (regardless of the brothers' sexual orientations). This does not appear to be true of boys with older step or adopted brothers. Each additional biological older brother increases the odds of a gay sexual orientation by as much as one-third.
- Various scientific studies across cultures have confirmed this finding. No such relationship has been found for lesbians regardless of how many older sisters or brothers they may have. What might be the reason for the "big brother effect"? Obviously, the male fetus in the womb hasn't the slightest idea how many brothers he has. But the child's mother's body does. Although the correlation between male birth order and sexual orientation is real, the reasons for it are more difficult to ascertain.
- The theory most often suggested by researchers relates to immune system in women. A few fetal cells can sometimes pass from the womb into the mother's bloodstream during pregnancy or the birthing process. Some researchers speculate that these cells interact with the mother's immune system and begin to develop antibodies against male fetal cells. The more male babies the mother has had, the stronger the immune response against them. Her body, then, at least in some cases, may react by changing something (probably the hormonal balance) in the uterine environment for later-born males that, in turn, leads to a tendency toward a gay sexual orientation.