Were-wolves and other were-creatures date back even beyond medieval times. In those days, however, were-wolves were not portrayed as biped animals, but as large ravenous wolves. The portayal of hairy men was made by Hollywood so it would be easier to disguise the actor. Some thought the were-wolf was a devil that had taken the shape of a wolf, or at least that it was one of Satan's servants. Gradually, depending on the regions, people began thinking that the unholy creature was a human that had turned into a wolf-like beast. In some parts of France, it was believed that the only way to kill a were-wolf was to shoot it with a silver bullet. People who had become were-wolves in the first place were thought to have been damned by God or had decided to serve the Devil. In the early colonisation days of Canada, settlers believed that you turned into a were-wolf if it had been ten years since the last time you had went to confession.

Even though these views seem to be purely superstitious, there were actual cases of were-wolvism, although these took more of a psychological approach. Many were-wolf trials had been held between the late 1400's and the early 1600's, similar to the witch trials. People convicted of being were-wolves or having their souls inhabit one were sure to be hanged or burnt on the stake. Most of these cases are well documented. Also, in those times there were medicine men, witches and sorcerers, who most of the time were the equivalent of present day malpractissing doctors. But back then, it was only guess work when it came to preparing the medicine. The drugs they would concoct would ofter be under or over potent. Someone would then come to them asking for some help whatsoever, and the witch doctor would give him a brew, a herb or an ointment that acted, unknowingly, as a hallucinogen or a psychedelic drug. The person would take the stuff and would then hallucinate, most of the time thinking he or she was a wolf. The person would then commit a murder, acting as a vicious animal. After comming back to his or her senses, the person would be then convicted of were-wolvism and, of course, in turn he or she would blame the person that administered the drug.

Another cause of hallucinations, more widespread this time, could have been caused by the kind of wheat that the peasants would use to make their bread. The peasants could not afford white flour as the rich could, and so had to substitute for a brown kind. This brown kind would contain a fungus during that grew during a certain time of the year, which would be unknowingly harvested along with the wheat. The fungus produced a toxin that would act as another hallucinogen to most people. This would then lead to the same effects as the witch doctor's drugs: the people would go out thinking that they were were-wolves.

In some ancient tribes around the world, some men would put on animal pelts and act peaceful or vicious, depending on the animal's temperament. In Africa, the famous "Leopard Man" cult consisted of men dressed in leopard pelts and steal claws, clawing their victims to death, thinking that they were actual leopards. But after a while, the leopard pelts served more as a disguise than to serve any religious purpose, the "Leopard Men" acting more like a gang and spreading terror to the neighbouring villages.
Even the term, "Berserk", comes from the Berserkers, a dreaded legion of Norsemen dressed in bear skins. The skins didn't just serve to symbolize the bear's strength, bravery, and to intimidate enemies, but the Berserkers would actually fight with the mad rage of a wounded bear, even when they were wounded themselves.
One more factor could of influenced the tale of the were-wolf: some families have found themselves to have had generations of members having hair covered faces. This strange case is due to a genetic factor.