What do King Arthur and breastfeeding have in common? Read on to find out.

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What if those Greek and Roman myths you read in high school weren't really stories? What if they were actually based on fact? It turns out that some ethnographers believe that the ancient gods and goddesses, people, places and events of religious lore are actually based on real people and things. This belief is called euhemerism, based on the work of Euhemerus, an ancient Greek scholar who was the first to posit the idea. Under the theory of euhemerism, Helen of Troy and King Arthur actually existed. However, their stories have been embellished to an exaggerated degree over the ages; they've come to more resemble fictional characters than real people.

The same theory can be applied to old wives' tales. One can argue that somewhere along the line, people noticed characteristics about the world around us and made note of them by folding them into nuggets of homespun wisdom that have been passed down from generation to generation.

Many of these nuggets concern pregnancy. Observations like a child carried low in the womb is a girl and darkened areolae means that a woman will have a boy are the result of years of predictions. These predictions may be based on original observations. Some of these would've been inevitably proven correct -- after all, there's a 50 percent chance the predictor is right. With enough accurate predictions, an observation might evolve into conventional wisdom.

The advent of the scientific method put a definitive end to many old wives' tales. At the same time, science has also shown that some old wives' tales about pregnancy and child rearing aren't too far off, and may even be correct. Anecdotal evidence, after all, is still evidence.

One of those tales involves the idea that a woman who's breast-feeding can't get pregnant. For the most part, this isn't true: Any woman with a regular menstrual cycle may become pregnant and many women get their first postpartum period while they're still lactating. There are, however, some conditions under which a woman can't become pregnant when she's breast-feeding. As old wives' tales go, this one is among the closest to the truth.

Learn about the physiological processes that led people to conclude that breast-feeding prevents pregnancy -- and why this doesn't necessarily work as a means of birth control -- on the next page.