When simple is a good explanation, go with it. Flesh means flesh. Barrenness and impotence is the exception not the rule. As discussed earlier, sex alone is not the creation of marriage. Here's a tangent- why are not two MEN joined together in sex become one flesh? the argument of being connected at the cellular level or even microchimerism could still apply, or even the "oneness" of agreeing with each other in every aspect of life could still happen. It is because the new life is never created. However being one-flesh with a prostitute(making a baby) is always a possibility(read that in "future tense"). Another thing, isn't the marriage really just a contractual changing of ownership, i.e. purchase and sale agreement? The reason for the exchange is the creation of new life or maybe another reason. Was Solomon truly married to(as in being in agreement intimately) his many wives? I think not, that is absurd on its face. Imagine his "servicing" each of his wives and concubines- "Sorry you didnt get pregnant this go around, see you in three years when your turn comes up again!"