Just for information, I want to mention the Celtic feast of “BELTAINE” (various spellings exist !) . It takes place on the “full moon of May”. It is a feast linked to the return of light and fertility.
One of the rites consists in women jumping over a fire, to ensure they get pregnant soon.
This sounds pretty much like the "But some cultures — including, allegedly, Australian aborigines — never got the picture. One writer says that as late as the 1960s ‘the Tully River Blacks of north Queensland believed that a woman got pregnant because she had been sitting over a fire on which she had roasted a fish given to her by the prospective father.’ "
Welcome to the Straight Dope Message Board, Jean-Pierre LAFAILLE. I assume you found us by way of the Straight Dope column, “When did mankind figure out that SEX = BABIES?”. Since our software doesn’t automatically tell us that, I’ll just put this link here so anyone who wants to read it can find it quickly.
Thanks for your input. I’d have to argue, though, that we have no reason to think the Celts didn’t understand Tab A into Slot B. But they knew that Tab A into Slot B doesn’t ALWAYS produce a baby. Blessings from the gods, however, might just do the trick, and showing your Celtic bravery by jumping a fire without flinching might make the gods pay attention and give you a blessing.
Plus, from all reports, there was a lot of sex going on around Beltane fires. (Still is, among neopagan groups today who observe Beltane.*) So you’d jump the fire with your sweetie and go screw, and then a baby’d pop out 40 weeks later. Imagine that! I don’t think (although I could be wrong about this, I’m not a scholar) that people were jumping the fire and then going home alone and wondering why no baby showed up.
Sounds like the claim of the Aboriginals is that intercourse isn’t necessary. If that’s true, I think it’s a little different from the Beltane theory, where intercourse is required, but augmented by ritual.
But, again, welcome and look around, and I hope you find more interesting stuff on the message board. Only a small part of it is comments on the Straight Dope Columns. There’s tons of user generated content, from Great Debates to Games; there’s bound to be some discussion you’d like to add to!
*Who, by the way, tend to spend lots of time during the modern ritual talking about fertility in its *metaphorical *sense, since most people who attend Beltane these days are not trying to get pregnant! We’re urged to consider “fertility” to mean creativity and productivity, and to use the Beltane energy to improve our art or business or gardens…that sort of thing. No Beltane babies for me, I’ve got a watercolor to work on! 
I think the English language contains traces of these notions too: an idea can be seminal, fecund or germinal.
Ooooh, I like that! I’m so stealing that for Beltane this year… Thanks!