Interesting you used the word “evolve”. So in theory you’re fine with the concept of marriage “evolving” between Judaism to Christianity, but it then it has to stop “evolving”? Why? Shouldn’t a concept like marriage be continuously evolving since what marriage entails continues to change over the course of humanity.

Another arguement is all the social and legal perks that marriage provides. Why would you deny this to people on the basis of how they have consenting sex with eachother? This creates a tier system where some relationships have more value than others for completely unjustifiable reasons.