In doing so he was attempting to settle a debate that has raged for decades: are gays born or made? It is a puzzle because homosexuality poses a biological conundrum. There is no obvious evolutionary advantage to same-sex relationships. So why are some people attracted to others of the same sex? Sexual attraction provides the drive to reproduction – sex is a means to an end not, in Darwinian terms, an end in itself. From an evolutionary perspective, same-sex relationships should be selected out.
Despite this, they are common in the animal kingdom. Birds do it, bees probably do it and fleas may do it, too. Among the many examples are penguins, who have been known to form lifelong same-sex bonds, dolphins and bonobos, which are fully bisexual apes. Various explanations have been advanced for the evolutionary advantage that such relationships might confer. For example, female Laysan albatrosses form same-sex pairs, which are more successful at rearing chicks than single females. Homosexuality may also help social bonding or ease conflict among males where there is a shortage of females. Gay couples will not preserve their own genes but they may help preserve those of the group to which they belong.