State-sanctioned marriage is a civil contract, period. A contract is not a judgment of moral value. It is a legal agreement between two parties that testifies to a meeting of minds between those consenting entities. It is not a religious act or rite and so has nothing to do with Adam and Eve or Steve or even Harvey.
It's hard for me to think of others because I'm not particularly in sympathy with the music of this century.
I've always regarded nature as the clothing of God.