You ever watch those movies (pre-historic, sci-fi.).
Example: Planet of the Apes (Charlton Heston one). All the man have beards, long hair, ect. The woman (Nova) has no hair, on her legs or under-arms. I guess it must be genetics. Or that the razor/shaver must have been invented by then….them.
Or
Characters shot with guns will fly backward, or upward and backward, through the air - the laws of physics notwithstanding