In Patrick Rothfuss' "Kingkiller Chronicle", a fantasy epic, the Adem are a nation of warriors where both sexes are equal. Apart from using sign language and being quite libertarian about sex, the women have the quirk that they do not believe that men have any influence about child bearing, they call it disparagingly the "belief of a man-mother". Their idea is that women "ripe" when they are ready and having regularly sex hides the constant gap of nine months. While the example is based on a fantasy epic, the idea is kind of fascinating.
Are there or have been any known cultures on Earth which really did not get it that men are necessary to create children?