Yevamot 46: Women Can't Be Circumcised

A long daf... When Jewish women became pregnant from partial converts (men who had been circumcised, but not yet dunked in a mikveh). Similar issues turn up with wine and cooking... So: decrees against the wine and the food, and that the children of such unions were mamzerim. All of which decrees by R. Yochanan do seem to be in line with his approach. Also, R. Eliezer's position on this status (circumcision without dunking) is that the person is a full conversion, and vice versa too. But the sages required both. But where are these principles derived from? Forefathers, foremothers? But women don't require circumcision. How do R. Eliezer and R. Yehoshua line up on this machloket? Plus, the generation that left Egypt and the issue of circumcision.