They did. It's called natural law, or the 'law of Nature and nature's God' in the Declaration of Independence.
Homosexuality is against the laws of nature.
You would think with such a high rate of death from doing well, unnatural things they would have figured that out.
Ahh, but married, man'n'woman couples can do some of those,
well, unnatural things too, y'know...
Sorry, had to point that out.
On another note... I talked to a divorce attorney about gay marriage, and he's against it... because he's got enough of a caseload with heterosexual divorces. You'd think a lawyer would salivate at the prospect of more work.