Is there any evidence or educated speculation that there was a time when humans believed conception to arise from means other than sexual acts? Or was it always common knowledge? Would this ignorance have predated homo sapiens sapiens?
Sigmund Freud mentions a certain Australian Aboriginal Arunta tribe in one of his books - Totem and Taboo, which according to him does not know, or does not believe, that pregnancy results from sex.
Quoting from the book:
The Aruntas have a peculiar theory about conception and re-birth. They assume that the spirits of the dead who belonged to their totem wait for their re-birth in definite localities and penetrate into the bodies of the women who pass such a spot. When a child is born the mother states at which spirit abode she thinks she conceived her child. This determines the totem of the child. It is further assumed that the spirits (of the dead as well as of the re-born) are bound to peculiar stone amulets, called Churinga, which are found in these places.