How do we know that rapes went unpunished or were not reported, for most of human history? One sure sign would be adaptations in women that are clearly for res

How do we know that rapes went unpunished or were not reported, for most of human history? One sure sign would be adaptations in women that are clearly for resisting or mitigating rape (like mallard ducks have) but there don't seem to be any such adaptations.