Well thinking of how it was before society's were a thing (and of the rapey dolphins), i assume, IF that is actually true, that the cause would be from males just fucking any woman they could, regardless of the woman's feelings. Since evolution is meant to continue the species, it's obvious it wouldn't care about the word "No" since by definition, that word is an END not a continuation. DNA is a hell of a thing.. Let's just hope with more time that we can overwrite that bit with something more societally acceptable.. TLDR; DNA is your old grandpa and Evolution is your nephew, Evolution tries to get DNA to use the latest Apple product called "Empathy", DNA respond's "If it ain't broke don't fix it!" and continues to use the last year model "Rape"..