The heritability of homosexuality is “only” 20%. That is, the probability that an identical twin raised independently will be homosexual if the other one is will be 20%.
First of all, that is much higher than the “normal” probability of 2-3%.
Hence, while homosexuality is obviously inheritable, it is not hardwired.
That raises a lot of question.
Let’s back to our first question. How can there still be gay people in the world.
It turns out that being homosexual does not decrease your gene pool survival rate as seriously as people have thought. What kicks you out of the gene pool is lack of success in mating with the opposite sex, not strong desire for to mate with the same sex.
In other word, impotence will kick you out of the gene pool way faster than bisexuality.
However, for most males, homosexuality is either a yes or no. While many women are bisexual, men are either homosexual or heterosexual with few between. At least according to Kinsey’s in http://en.wikipedia.org/wiki/Kinsey_Reports.
Still according to Francis statement, heritability of homosexuality is only 20%. So whatever genes that “cause” homosexuality will only kick you out of the gene pool 20% of the time, at most. That gene may come in package with other edge, like better male bonding skills, or better artistic skills, etc.
All in all, we have impotence, suicidal, and poor males. It’s not strange to see gay people as a normal variation. In fact, homosexuality won’t hurt your gene pool survival much more than say, monogamy. The former will simply reduce the number of your potential mate from 1 to 0, rather than the normal number of 1000.
What truly surprises me is why so many religious bigots oppose homosexuality so much?
I’ve never heard religions condemn impotence, or lack of money making skills, or lack of promiscuity.