Adam (and Eve) would have had a bellybutton if God himself has one, since it's said that He made Adam in His own image. However, since nobody knows what God looks like, regardless of whether or not you believe in any kind of religion, I'm going to be inclined to say that whether or not they originally had them, I'm betting they probably did once they were cast out of the Garden of Eden since Eve was condemned to long torturous childbirth...which makes me wonder if they even had reproductive organs before that. I mean, God doesn't reproduce, does He? So why would Adam and Eve have been created with them?