In the 10,000 or so years since human beings became civilized, virtually every culture in the world has referenced supernatural monsters in its folk tales--and some of these monsters take the form of scaly, winged, fire-breathing reptiles. "Dragons," as they're known in the west, are usually depicted as huge, dangerous, and fiercely antisocial, and almost always wind up being killed by the proverbial "knight in shining armor" at the end of a back-breaking quest.
Before we explore the link between dragons and dinosaurs, it's important to establish exactly what a dragon is. The word "dragon" comes from the Greek "dracon," which means "serpent" or "water-snake"--and, in fact, the earliest mythological dragons resemble snakes more than they do dinosaurs or pterosaurs. It also helps to know that dragons aren't unique to the western tradition; these monsters feature heavily in Asian mythology, where they go by the Chinese name "long."
What Inspired the Dragon Myth?
Identifying the precise source of the dragon myth for any particular culture is an impossible task; after all, we weren't around 5,000 years ago to eavesdrop on conversations or listen to folk tales! That said, though, there are three appealing possibilities:
Dragons were mixed-and-matched from the most frightening predators of the day. Until only a few hundred years ago, human life was nasty, brutish and short, and many people met their end at the teeth (and claws) of vicious wildlife. Since the details of dragon anatomy vary from culture to culture, it may be that these monsters were assembled piecemeal from familiar, fearsome predators: for example, the head of a crocodile, the scales of a snake, and the wings of an eagle.
Dragons were inspired by the discovery of giant fossils. Ancient civilizations could easily have stumbled across the bones of long-extinct dinosaurs, or the mammalian megafauna of the Cenozoic Era. Just like modern paleontologists, these accidental fossil-hunters may have been inspired to visually reconstruct "dragons" by piecing together bleached skulls and backbones. As with the above theory, this would explain why so many dragons are "chimeras" that seem to have been assembled from various animals.
Dragons were based on recently extinct mammals and reptiles. This is the shakiest, but the most romantic, of all dragon theories. If the very earliest humans had an oral tradition, they may have been able to pass down accounts of creatures that went extinct 10,000 years ago, at the beginning of the Ice Age. The dragon legend could have been inspired by dozens of creatures, ranging from the Giant Sloth to the Saber-Tooth Tiger to (in Australia) the giant monitor lizard Megalania, which at 25 feet long and two tons certainly attained dragon-like sizes!
Dragons, Dinosaurs and Christian Apologists
The above are the three likeliest explanations for the dragon myth. Now we come to the unlikeliest, but also the most popular (at least in the U.S.): the insistence by Christian fundamentalists that dragons actually *were* dinosaurs, since dinosaurs were created, along with all other living creatures, only about 6,000 years ago.
It's hard to categorically refute an argument based on such an outlandish claim. If, for example, you say that carbon dating proves Tyrannosaurus Rex roamed the earth 65 million years ago, a fundamentalist might counter that modern science was created by Satan as a way to deceive unbelievers. By the same token, if you point out that Noah's Ark was too small to accommodate even a small fraction of known dinosaurs, a clever apologist will insist that Noah took along dinosaur eggs, not real, live dinosaurs!
Amusingly, some creationists have tried to meet modern scientists on their own terms, with an account of how dinosaurs (that is, dragons) breathed fire. According to this story, dinosaurs belched the methane gas produced by their capacious digestive systems, then ignited it by gnashing their teeth! To support this argument, fundamentalists cite the well-known example of the bombardier beetle, which somehow evolved the ability to squirt a noxious, boiling, irritating chemical out of its rear end. (That's where their victory ends, though; there isn't even a shred of evidence that dinosaurs breathed fire.)
Dinosaurs and Dragons in the Modern Era
There aren't many (or any) paleontologists who believe that the dragon legend was invented by an ancient human being who glimpsed a living, breathing dinosaur and passed the story down through countless generations. However, that hasn't prevented scientists from having a little fun with the dragon myth, which explains recent dinosaur names like Dracorex and Dracopelta and (further east) Dilong and Guanlong, which include the "long" root corresponding to the Chinese equivalent of "dragon." Dragons may not have really existed, but they can still be resurrected in dinosaur form!