Assignment task: What causes homosexuality? The facts so far seem to be these:
Homosexuality does appear to run in families.
Identical twins are more likely than fraternal twins to share a homosexual orientation.
Men with a greater number of older brothers are more likely to be gay (about one-third more likely for each older brother). The same is not true for adopted brothers.
Which of these facts is evidence for a genetic component?
Which of these facts is evidence for an environmental (prenatal) component?
For which is it unclear (could be either or both)?
Briefly explain your rationale for each of the above replies.