Describe the evidence for the genetic and/or biological basis for homosexuality, as well as the evidence for the environmental influences on sexual preference

What will be an ideal response?

Homosexuality appears to run in families, with concordance rates for homosexuality more common among identical twins than fraternal twins or siblings. Other evidence suggests that homosexuality is associated with differential exposure to hormones in utero. Research also suggests that the structure of the brain may differ in homosexuals. However, temperamental factors may also interact with environmental factors to produce sexual orientation. Bem (1996) argues that those things that seem exotic tend to become erotic. In support of environmental influences, even identical twins don't always have the same sexual orientation, and boys with an increased number of older brothers are more likely to be gay.