It's a well-known fact that Early Modern Europe, most especially Britain and Germany, saw a wave of panicked trial and execution of an unexpectedly high number of people, mostly women, thought to be witches. What's perhaps more surprising is that this first seems to manifest, not from an attempt to destroy some subterranean magical cult as imagined by Margaret Mead, nor from a generic McCarthy-like fear of infiltration by the enemy as in Miller's famous theatrical depiction of witch trials in colonial America, but from a highly specific sort of hysterical panic on the part of men. Witch trials in sixteenth-century Europe seem, based on the writings of those involved in them, to have been about an unusual male fear which has prompted similar outbreaks of judicial or extrajudicial violence around the world, including in the present day.
The central idea of the witch panic, in its earliest days, was the fear of having your penis stolen. From this bizarre beginning, Europeans launched themselves into a frenzy of torture and execution of alleged witches which lasted centuries.
One might argue that this fear is a manifestation of a concern about loss of status, loss of sexual control, the fading of a patriarchal system, or something deeper along those lines. It's a question that's been raised by anthropologists, and the only consistent conclusion is this: whatever the underlying cause, it's specifically manifested itself time and again in men being terrified that women are, by some eldritch means, either removing their penises entirely or causing them to shrink until nothing is left. There's even a term of art for epidemics of such fear: it's called a penis panic.
The Malleus Maleficarum, or "Hammer of Witches", is a text for witchfinders, by witchfinders. Published in 1487 by the German priest Heinrich Kramer and based on the claims alleged witches were forced into making under torture, it lays out an explanation of how witches are people, usually women, who have sex with the devil in dark ceremonies they travel to by magical means. We're then treated to a discussion of the many sinister things a witch might use diabolical powers to achieve. They're capable of turning people into animals, and of making crops fail and livestock die, but far more ink is spilled explaining the nuances of magical penis theft. The authors tell us how witches can make men's penises disappear entirely, or just shrink, how they can steal them and use them for their own unspecified purposes (which is the only hint that these imagined penile assaults might have any motive at all), and how they can also hex a man's mind to make him *believe* his penis is shrunken or missing when it is intact. Advice is even given on how to tell the difference between when a witch has stolen a penis and when she has merely cast an illusion to make it seem to be missing; presumably if this needs to be ascertained by means other than looking under the man's trousers, the illusion also deceives other observers. (In this concern the Malleus Maleficarum is particularly detailed, but not unique in the accusation, which is first attested in 1475 and is mentioned a few other times in the late fifteenth century.)
Penis panics have been reported in many other cultures. In present-day southern China and other parts of southeast Asia, shrinking penis syndrome, or koro, is a medical condition whose sufferers perceive that their penises are slowly retreating into their bodies and will ultimately disappear; no externally-visible change in the penis is reported. There's normally an accompanying fear that when the penis fully retracts, death will result. (Traditional Chinese Medicine attributes shrinking penis syndrome to a depletion of male energy, and regards the shrinkage as entirely real.) It's not especially common, and it is unique to those cultural contexts. There was an especially serious outbreak of koro in Singapore in 1967; at its peak, 97 men checked into emergency rooms in a single day to have their penises treated for the condition, which was widely believed to result from eating pork from pigs vaccinated against swine flu. A folk remedy suggested tying a red string around the organ to prevent further shrinkage; in at least a few cases, these strings were tied tightly enough to cause genuine physical harm to the man.
More recently, a late twentieth and early twenty-first century penis panic struck central and west Africa. In this instance it was generally supposed that an apparently-innocuous brush with a stranger triggered the event, after which the man's penis began to shrink or retract immediately; this was generally supposed to have been deliberate on the part of the non-victim, and in some cases it is reportedly possible to perceive the start of the shrinkage immediately. In some cases, the victim promptly cried out for the crowd to help them apprehend the apparent perpetrator, as one might with a pickpocket; in Ghana, the resulting mobs killed at least a dozen people in the 1990s. In Congo the following decade, local police even regularly arrested people for sorcery who were accused of stealing penises, which at least had the effect of protecting the purported perpetrators from vigilantism.
In this the modern African cases echo the Early Modern witch hunts - but they don't have anything like the body count. However, the European cases involved an entire mythology of witchcraft of which the genital anxiety was only one aspect; it's not clear how frequent reports of vanishing members actually were. Certainly, however, the fear that such assaults were possible helped fuel the witch hunt craze, which claimed an estimated 40,000 lives across Europe and its colonies in a span of four centuries. Not all of these trials were related to penis panics, which seem to have faded by the year 1500 (no record of genital theft is found in the testimony at the Salem witch trials, for example), but the sexually-oriented Malleus Maleficarum and its attendant mythology remained in wide use among those responding to witchcraft hysteria through the eighteenth century. There is, of course, no evidence that any of the alleged victims were in fact affected by any kind of magic, or that any man's penis has ever actually vanished, but the deaths which resulted from the fear were no less real.
The "Great Witch Craze" of the Early Modern period most likely began as a result of the crisis of the Late Middle Ages, when a series of epidemics, famines, and the climate change which marked the start of the Little Ice Age wreaked havoc on European economies and there was a need to find somebody to blame. And it appears that manifested in part in a curious hysterical form that it is difficult for modern Westerners to make sense of, with a German penis panic that would ultimately shape the subsequent mythology of witchcraft. But even absent the initial cause, the inclination to find others who can be scapegoats for all manner of problems, real and imagined, is an all-too familiar aspect of human psychology across time and space; by the time things had gotten into full swing, the witch hunts were self-sustaining to a large degree. By the point where witch trials were at their peaks the initial epidemic of apparent genital shrinkage was long since over, but all manner of other problems were being blamed on the witches.
The madness hit its peak during the European Wars of Religion, though it had begun over a century earlier and continued for over a century after. During this time, both Protestant and Catholic territories executed witches in significant numbers, though in both there were writers who thought the practice barbaric and the belief in the power of the witches heretical; such writers tended to attribute the witch craze to the other group, with the voices of reason among the Protestants seeing witch trials as another excess of the Inquisition and its ilk while Catholic writers pointed to the official church position that diabolical magic is impossible and thus attributed the belief and attendant deaths to Lutheran heresy. While historians to this day debate which group was more severe in its persecution of alleged witches, it's clear that despite sporadic calls for restraint and level-headed justice from all corners, both continued to pursue witchcraft with abandon.
That so many could perish in so obviously misguided an internal crusade shocks us today, as it should, and often makes us seek out reasons by which to make sense of it. Poorly-supported hypotheses involving ergotized bread or eccentric wise women making easy scapegoats may in reality explain a few of the particular witch trials, but they aren't enough, given the grand scale of the phenomenon. They are also probably not necessary, but they gain some popularity because they have a feature the most probable truth lacks: a promise that it is unlikely to happen again. The reality, it seems, is that a particular epidemic of a curious mental disease likely touched the whole thing off, but that not even illness was necessary to keep it going; once we begin to see witches among us, it's very hard to stop.