Homosexuality, to oversimplify greatly, is when a member of a presumptively binary gender is sexually attracted more or less exclusively to other members of the same gender, rather than to members of the opposite gender.
The role of homosexuality – or, more properly, sexual orientation – in evolution is not known, as the mechanisms behind it are not well understood. It is known that it is more or less fixed at a very young age, but there do not seem to be specific genetic characteristics associated with it. In layman's terms, there is no "gay gene".
The role of homosexuality in human reproduction is largely a positive one. While gay couples can conceive -- either by having sex with members of the opposite gender specifically for the purposes of reproduction, or else by artificial insemination (for women) or purchasing the services of a host-mother (for men) -- they must do so deliberately, since they are far less likely to be involved in sexual activities that might result in conception.
Further, gay couples are far more likely to adopt than hetero couples. (This is certainly understandable, given their lack of fertility with each other. Regardless of what method they choose for reproduction, none of their children will be the biological offspring of both members of a gay couple.)
In other words: homosexuality is pretty much an unalloyed benefit to humanity. Gay people have next to zero unwanted pregnancies, are a major source of good homes for unwanted children, and overall help to slow population growth.
Fundamentalist branches of various religions hold that homosexuality is a bad thing, and prescribe various sanctions against it. These include:
- Homosexuality is a sexuality issue.
- Many people think same-sex marriage should be (as it currently is, in much of the United States and in some other parts of the world) illegal.
- homosexuality and religion: Many religious groups (especially Christian and Islamic fundamentalists) are vehemently opposed to homosexuality, while other religious groups show varying degrees of tolerance and support for it.
- Social conservatives may also be anti-gay, believing that homosexuality threatens the established social order.
- BornDifferent.org: advocacy site based on the theory that homosexuality is biologically-based
- No Moo Lies: counterargument site by Focus on the Family
- Lambda Legal: organization fighting sexuality-based discrimination
- 2014/04/07 [L..T] Not Your Tragic Queer Muslim Story
- 2014/03/08 [L..T] Lebanon Just Did a Whole Lot More Than Legalize Being Gay
"If homosexuality is a disease, let's call in queer to work." (seen here)
Parts of this article were originally posted on Google+ in response to Christian anti-gay claims.