The modern monsters we see depicted in pop culture — which regularly capture fascination and inspire fear, thrill , and wonder in people across the world — have evolved over time to become what they are today.

From ancient myths to YA romance trilogies, here are some amazing historical and scientific facts about your favorite monsters.

Vampires

These blood sucking, coffin-dwelling anthropomorphic bat-humans of the night have origins in ancient history, gained notoriety in the fiction Dracula, and earned modern sparkly popularity in young adult fiction.

Though the term “vampire” wasn’t coined until the mid-18th century, these creatures have been regarded in myth, typically as demonic or supernatural beings, in Asian, Egyptian, Mesopotamian, Indian, European, African, and American folklore.

Bram Stoker’s Dracula, written in 1897, is based off of Romanian prince Vlad Tepes. Also known as Vlad the Impaler for his execution method of choice, the historical figure did not drink blood, but was regarded a national hero by Romanians.

The name “Dracula” is derived from the Romanian word drac, which means either dragon or demon, with ulea meaning “son of.” Vlad’s father founded a secret fraternal order of knights called Order of the Dragon.

A 2014 discovery claims to have uncovered the dungeons in which Vlad the Impaler was held hostage by Ottomans in present day Turkey.

Networks of self-professed vampires exist today — participants in this subculture either consume blood from donors or claim to draw “spiritual nourishment” from human energy instead. Human consumption of blood, however, is toxic, and can lead to liver and nervous system damage.

Werewolves

Humans that transform into wolves when the moon is full are a Halloween and Hollywood staple, having manifested in everything from American Werewolf in London, to Twilight, to 30 Rock’s werewolf bar mitzvah.

Also known as lycanthropes, the legend of werewolves can be traced back to ancient mythology, in which various references of men transforming into wolves can be found. One such story of a man turned into wolf as a punishment for eating human meat was written in 1 AD.

In 16th century Europe, what were thought to be werewolf attacks lead to a panic over which several men were executed. Some incidents may have mistaken actual wolf attacks for werewolf attacks, but at in at least one case (most notably that of Peter Stumpp, Werewolf of Bedburg), werewolves were used as an explanation for cannibalistic serial killers.

In non-Western cultures, belief in werewolf equivalents, such as were-leopards, were-pumas, or were-hyenas fill the niche of regionally feared predatory shape-shifters.

Many superstitious causes of lycanthropy have been noted throughout history, including conception under a new moon or consumption of certain herbs or water touched by a wolf — of these, transformation under a full moon has stuck most consistently to the legend. (Full moons have been thought to cause odd behavior in people and animals, but the supporting science is inconclusive.)

There are several recognized medical conditions that explain werewolf-life behavior: one is hypertrichosis, which causes growth of unusually long hair on the face and body; another is clinical lycanthropy, which may cause a person to believe they have been transformed into a wolf or other animal.

Ghosts

From Macbeth, to Charles Dickens, to GhostBusters, spirits of the dead left to linger among mortals are a tireless point of fascination and thrill in entertainment and folklore both modern and ancient.

Recorded sightings, visitations, or hauntings by spirits of the dead persist throughout all of recorded history. Early references include the Hebrew Bible and Egyptian Book of the Dead.

The practice of “ghost hunting” began with the emergence of Spiritualism in the mid 1800s, with an organization called The Ghost Club formed in London in 1862, which has been investigating paranormal occurrences ever since. Today, TV shows like the Ghost Hunters televise such investigations.

A 2013 Harris poll found that 42 percent of Americans believed in ghosts. According to Pew Research, 18 percent of Americans believe they have seen a ghost, and 29 percent have felt at some point in touch with someone that had died.

Scientific explanations for ghostly phenomena include hallucinations, electric brain stimulation, the ideomotor effect (power of suggestion), drafts, camera problems, and ionic energy.

Zombies

The reanimated, brain-eating corpse has been all the rage in pop culture this decade, as prevalent in television and video games as it is in the nightmares of children.

The idea of zombies traces back to 8th century Haiti, from the word “nzambi” or “zombi”, which referred to persons brought back to life without speech or free will (typically as mindless slaves) by ancient Voodoo practices.

It’s attested that this zombie-like state was induced by the administration of a combination of poisons, including venom from toads and puffer fish, followed by the hallucinatory drug tetrodotoxin, which suspends animation.

The concept of a zombie apocalypse, however, in which society breaks down as a result of a zombie outbreak, is a newer phenomenon. It began with the 1968 film Night of the Living Dead, which popularly depicted for the first time zombies as ghoulish, contagious, man-eating plague monsters.

Two scientists have applied a neurological disorder called Consciousness Deficit Hypoactivity Disorder to diagnose fictional zombies, a term they coined to explain the brain functions or damages causing a zombie to hypothetically eat flesh, lumber about, and lack basic intelligence and motor skills.

Thought experimenters say a zombie outbreak is not impossible, however improbable. Weaponized parasites, brain fungus, Mad Cow-like diseases, and neurotoxins are all theoretical culprits that could, under the worst of worst circumstances, turn the human population into mindless “walkers.” Luckily, the CDC can prepare you for that.

Originally published on October 30, 2014.