Sex and procreation can be found throughout recorded human history, regardless of locale. In mythology (from Zeus boning anything that moved to "be fruitful and multiply" to the Immaculate Conception and numerous creation myths besides), religious teachings regarding sex being for procreation and not mere pleasure, laws governing property rights, inheritance and royal succession, in literature, in plays and songs, in fairy tales and old wives' tales, etc.

For example, here's an article on Samuel Pepys and a sexual manual from 1680 which quite clearly demonstrates that the nature of carnal knowledge was generally known at the time[0]. Along with death and mortal fear, sex and birth comprises one of the archetypal constants of the human experience. It's everywhere. It also happens to be knowledge that's necessary to continue the species, which humans have proven quite good at.

I guarantee that our parents knew how babby was formed, as did their parents, as did their parents, etc. Even our hominid ancestors before the formation of language understood it, because even animals understand it at an instinctive level.

[0]http://theappendix.net/posts/2013/06/this-misterie-of-fuckin...

I'm pretty sure neither I, nor the comment to which I was replying was referring to the knowledge (or ignorance) of the link between sex and pregnancy. At least in general.

The problem for something like contraception, which is the context here, is in understanding the details. Those details are sorely lacking in plays, songs, fairy tales, and old wives' tales.

> It also happens to be knowledge that's necessary to continue the species

No knowledge is actually necessary, as mere ignorant performance of the act is sufficient.

Right, just because some proto-scientist in a primitive ivory tower had observed two goats fucking, doesn't mean the common person had access to that kind of knowledge.