God made Adam and Eve, not Adam and Steve.
God didn't make anyone. Humans made god, in their minds.
Even if (for the moment) you believe in Evolution
It's not a matter of believing in evolution or not, it's a matter of rejecting the strong evidence for evolution because you're a deluded biblecigarette or not.
how will marrying someone that you cannot reproduce with help your species?
Here we go with this redundant argument. Humans do plenty things all day every day that aren't "natural" to the species. If you're going to use that to argue against gay marriage, then we have to use it against movies, music, video games, recreational love, posting on this forum. None of those advance the species, they are all for entertainment. How is marrying somebody you love, who happens to be the same love, any different?
