Board Thread:General Discussion/@comment-5413572-20160521065337/@comment-26887879-20160522114430

Well, in the intro which shows flashbacks of Human and Monster war, Monsters look super tall compared to adult humans and when we look at the sprites, Papyrus is the shortest of "tall" main characters while Sans is almost same height as Frisk/Chara. The only humans we see are Frisk and Chara,  the two look wery simmilar to each other and it's implied both of them are children. Also, height comparation between them and Asgore is simmilar to Boss Monster and Humans from the intro picture, but it also might be due to different art styles...

Undertale is pretty cartoony universe with simple art style, while Monsters have drastic body shape differences, Human sprites might be all almost the same, like for example in Pokemon games, but that might be wrong... We sadly don't know, since we never see other humans...