Some tribes in remote areas of the globe, who lived under primitive communal regime in the 20th century. Suppose, they did not associate childbirth with sex at all, they regarded it simply as a characteristic of women.
An opinion put forward by Malinovsky at the beginning of the 20th century, and since then repeatedly challenged: he simply misinterpreted the responses of the locals. At least further studies in other tribes have consistently shown that the Aborigines are well aware of the existence of connection, although they do not understand the underlying biology.