I'm planning to do a story that involves other branches of humanity surviving (H. erectus is as far back as I'll go), and I'm striving to be fairly accurate with my representations. There is however one issue that I'm not sure if there's an answer to. Simply put, when permanent breasts evolved in the human lineage. I mean to my knowledge no other apes have them, yet is seems like artists tack them on as soon as the species their drawing is separated from chimps. Does anyone have an idea when they evolved, or is it one of those mysteries of soft tissues that might never be solved?