Have learned that heels originated not in women's shoes but in men's, specifically, used by Persian riders so as not to slide from the stirrups. Later men elevated themselves as a sign of status. The word "wealthy" came from "well heeled." Women, not to be outdone, started wearing heels too. Heels particularly flourished during Louis XIV's reign, although nobody was allowed to wear heels higher than the king (5 inches).
Another interesting aspect: the heels in women's shoes were positioned at the instep, as you see in the picture above. That was designed to force women to walk small dainty steps (it was highly uncomfortable and threw them off balance), thus appearing poised and unhurried and restricted in their huge floor-long skirts. Men, on the other hand, were permitted freedom of movement, and soon abandoned heels to differentiate themselves from women who really took on the fashion.
I wonder how much more I will uncover by reading about the history of ballet. I want to share the whole book with you. Every page leaves me gasping and exclaiming, "OMG, I DID NOT KNOW THAT."