Dragons are among the most popular and enduring of the world's mythological creatures. Dragon tales are known in many cultures, from the Americas to Europe to India to China. Though they populate our books, films, and television shows, they have a long and rich history in many forms.

It's not clear when or where stories of dragons first emerged, but the huge, flying serpents were described by the ancient Greeks and Sumerians. For much of history dragons were thought of as being like any other exotic animal: sometimes useful and protective, other times harmful and dangerous. That changed when Christianity spread across the world; dragons took on a decidedly sinister interpretation and came to represent Satan. In medieval times, most people who heard anything about dragons knew them from the Bible, and it's likely that most Christians at the time believed in the literal existence of dragons. After all, Leviathan - the massive monster described in detail in the Book of Job, chapter 41 - seems to describe a dragon in detail:

“I will not fail to speak of Leviathan's limbs, its strength and its graceful form. Who can strip off its outer coat? Who can penetrate its double coat of armor? Who dares open the doors of its mouth, ringed about with fearsome teeth? Its back has rows of shields tightly sealed together; each is so close to the next that no air can pass between. They are joined fast to one another; they cling together and cannot be parted. Its snorting throws out flashes of light; its eyes are like the rays of dawn. Flames stream from its mouth; sparks of fire shoot out. Smoke pours from its nostrils as from a boiling pot over burning reeds. Its breath sets coals ablaze, and flames dart from its mouth.” (NIV).

The belief in dragons was based not just in legend but also in hard evidence - or so it seemed. For millennia no one knew what to make of the giant bones that were occasionally unearthed around the globe, and dragons seemed a logical choice for people who had no knowledge of dinosaurs.

Though most people can easily picture a dragon, people's ideas and descriptions of dragons vary dramatically. Some dragons have wings; others don't. Some dragons can speak or breathe fire; others can't. Some are only a few feet long; others span miles.

Some dragons live in palaces under the ocean, while others can only be found in caves and inside mountains.

As folklorist Carol Rose discusses in her book Giants, Monsters, & Dragons: An Encyclopedia of Folklore, Legend, and Myth (Norton, 2001), dragons “have composite features from many other beasts, such as the head of an elephant in India, that of a lion or bird of prey in the Middle East, or numerous heads of reptiles such as serpents. Their body color may range from green, red, and black to unusually yellow, blue or white dragons.”

Zoologist Karl Shuker describes a wide variety of dragons in his book Dragons: A Natural History (Simon & Schuster, 1995), including giant snakes, hydras, gargoyles and dragon-gods, as well as more obscure variants such as basilisks, wyverns and cockatrices. The dragon, whatever else it might be, is clearly a chameleon, its features adapting to the cultural and literary expectations of the era.

Dragons continue to capture the public's imagination in fantasy books and films, appearing in everything from the kid-friendly 2010 film How to Train Your Dragon to the more adult-oriented Game of Thrones books and to The Hobbit book and movies. The popular role-playing game Advanced Dungeons and Dragons describes more than a dozen varieties of dragons, each with unique personalities, powers, and other characteristics (Black dragons, for example, are fond of eels - who knew?).