Yesterday, Today and Tomorrow

I was discussing some stuff online with a group of people and the subject turned to God and the bible and one of them said something along the lines that the bible was written to help humanity in a time that was very different than this one and that as humanity evolved then so too should the moral codes.

Now think about that, it's great for those arguments where we want to justify doing whatever you want and calling it evolution but what about the other stuff? What about the promises? What about salvation? You can't have one without the other.