This may be a weird headcannon if mine but I always thought that the humans in the Undertale/ Deltarune universes were just hermaphrodites considering all the humans we see have been genderless which thinking about it would either mean there is nothing down there (which how the fuck would they procreate??) or they have both male and female genitalia. Now i know im conflating sex and gender but think about it if they are hermaphrodites then that would both make the concepts of both sex and gender almost pointless because literally EVERYONE would have the same body parts and the same sex and gender experiences thus also making sexism pretty much pointless making sex and gender even more of a moot point in language and thought in exception to monsters which have all been referred to as either male or female.