Did Adam have a belly-button? I believe we really have an answer to that, and we can say, 'No — Adam didn't. Neither did Eve.'
Why? Because your belly-button (navel), or tummy-button as it's sometimes called, is a sign that you were once attached to your mother. You depended on that life-line — the umbilical cord — for your nourishment from her body as you developed inside her.