I think one of the most comforting things about really old artwork is that people back then walked around naked all the time, too. Still, I think ancient art classes had to pay models for their time and energy. It probably took longer, too, because you couldn’t “take a picture, whydoncha”. If only those first nude models had any idea how many millions of people would be seeing their “art supplies” throughout history, they probably would have rethought that half credit towards their art major.