At today's oral arguments in Obergefell v. Hodges (the marriage cases), some Justices expressed concern with concluding that the Constitution prohibits marriage bans when no state allowed same-sex couples to marry until 2003, and that they could not think of a society in history that had allowed same-sex couples to marry.
It seems that gets things backward. It's not like throughout recorded history, gays and lesbians have been treated well but for the itty-bitty fact that we were not allowed to marry the people we loved. In fact, the opposite is true. For much of history, gays and lesbians have been stigmatized, tortured, scorned, cast out, etc. by the governing forces in their societies, both church and state. American society from our founding is far from immune from this indictment.
It is hardly a surprise that societies that suppress a minority don't establish institutions like marriage to take that minority's needs into account.
The absence of marriage equality in much of human history is not a rationale to continue to deny this fundamental right to same-sex couples. Oppression does not warrant continued oppression under the U.S. Constitution's Equal Protection Clause. Exactly the opposite is true: A history of oppression warrants heightened scrutiny of laws that harm the targets of historical oppression.