I'm getting bored by ignorant Christians, or even non-Christians, who sanctimoniously proclaim that their only objection is to gay marriage lies in the fact that "for thousands of years, by all cultures and all religions, marriage has been defined as a union of one man and one woman."
It should be obvious to anyone with half a brain or half a semester of anthropology that such a view is an utter lie.
Marriage across the globe, even today in this modern world, is still largely polygamous, especially in the African and the Muslim worlds.
Christians, in expressing this idiotic sentiment, demonstrate that they don't know their own Bible, which is quite explicit that all the Patriarchs had, if not multiple wives, then certainly what we would only think of as harems. Much is made in the Bible of Sarah's infertility, and how at 90 years old she finally gave birth to Isaac. But how do Christians ignore Abraham's five other sons by women other than Sarah?
We read also of the handmaid Hagar, and her son Ishmael, regarded universally as father of the Arab race. Solomon famously had 700 wives and 300 concubines. His father David had an untold number of wives - enough that he built a number of palaces for them. The story of Absalom's revolt against his father David includes the tale of David fleeing his palace and leaving 10 of his wives behind. When Absalom occupied the palace, in a demonstration of his manhood, he had his way with each of those 10 wives on the roof of the palace, in full view of the Israelites.
After Absalom was killed and David moved back into the palace, he built a special house for those 10 wives, from which they never were allowed to set foot as long as they lived. Seems a little harsh as it wasn't their fault, but throughout the Old Testament, women get the short end of the stick.
The point being, marriage as a mutually monogamous union between one man and one woman is a minority opinion and a relatively recent development in history. There have even been recorded a very few polyandrous societies, in which women have multiple husbands. Biologically, this doesn't make very good sense, which is why there haven't been more of them, and yet they've existed.
Opposing gay marriage on the basis of a "thousands of years" old definition of marriage, and a mistaken definition at that, isn't good history. It's not even good Biblical Research (as if that should matter when forming public policy).
Islam allows a man up to four wives. The Prophet Mohammed had 11. All but two were widows of his cronies whom he married to care for. He seems to have been devoted to his first wife, who was about 15 years older than he was, but she died fairly early after he launched his career as a prophet. Mohammed didn't start collecting widows until after she died. Once he did, however, he apparently liked them young. He picked his last wife, Aisha, when she was six and married her when she was nine years old, and according to stories, she lorded it over the rest of Mohammed's harem.
Pretending the mainstream Christian definition of marriage is the only definition of marriage is preposterous. Even Christians, judging from their own Holy Book, plainly have never been able to determine a single definition.
Ultimately, it shouldn't matter. Let each religion or religious denomination define marriage as they wish with the confines of their own beliefs. No matter how backward or how medieval. The STATE, on the other hand, that's another matter.
The state - civil society - should treat all its citizens equally and grant them licenses to combine their life affairs in prescribed ways not determined by the whims and vagaries of superstition. Inheritance, insurance, medical visitation, next-ofkinship, taxation and the numerous many rights that spring from State Recognition of marriage -- these are the things like that gay people are concerned about. Some of them are obvious - social security, for instance, or joint income tax filings. Some are less so, but taken for granted by straight people. I don't, for instance, particularly want to testify against my partner in court.