Petrus Gonzales (1648), the first recorded case of hypertrichosis. Public domain.

The werewolf legend — and shape-shifting in general — is quite possibly as old as civilization itself. How Stuff Works points to “The Epic of Gilgamesh,” one of the oldest written works, as a possible “first mention” source for werewolves. Gilgamesh discovers that the goddess Ishtar — who has amorous designs on his virtue –turned one former lover (a shepherd) into a wolf. Gilgamesh wisely refuses her romantic overtures.

Ovid’s “The Metamorphosis” tells the story of King Lycaon of Acadia, who is visited by the god Jupiter in disguise and dares to serve human flesh to the immortal. Jupiter frowns on cannibalism, it turns out, so he turns Lycaon into a wolf. It’s not a coincidence that his name comes from lykos, meaning “wolf” — which is also a root word for lycanthropy, the delusion wherein someone believes he or shehas been transformed into a wolf or other kind of animal.

The earliest film about werewolves is The Wolfman, in which those bitten by a werewolf transform into the same half-human, half-wolf hybrid.

Originally, the transformation took place in the autumn, commonly the season when monkshood or wolfsbane is in full bloom. People in the movie attach wolfsbane flowers to their clothing to ward off attacks, but in reality, the plant is very poisonous so it wasn’t the smartest protective mechanism. Those who work with these plants typically wear gloves and give their hands a thorough washing after.

In the Twilight series, Jacob Black’s unique condition runs in the family, and it turns out that there is a genetic disorder called hypertrichosis that gives rise to excessive hair growth, in the most extreme cases all over the body. It is sometimes called “werewolf syndrome,” and may be the root of the werewolf legends.

Read more here, at Scientific American.