Does the case for same-sex marriage have implicit religious assumptions?

The case for same-sex marriage seems to be based on equality. But one could certainly argue that any argument based on equality has underlying religious premises. The Declaration of Independence says that we were created equal, which, of course would be false if we were not created. And we certainly did not evolve equally, nor would it make sense to say that we were endowed by evolution with certain inalienable rights. So, if atheistic evolution is true, and we were not created, would that not provide a basis for supporting the race, sex, or sexual orientation that one considers to be superior?