Those are of course fake buttons, they had plastic surgery to avoid the crushing social pressure of, hmm… themselves i guess?

I assume the implication here is that they have belly buttons, because at some point, both Adam and Eve had an umbilical cord attached to them, which in turn would mean that they weren’t the first man and woman, but someone else was.

I’m thinking Occam’s razor applies here: the artists simply weren’t thinking that far ahead when painting those pictures.