Dracarys!

Anthropologists at UMass-Amherst have determined that ancient dragon myths are very common and have identified over 400 dragon myths on every inhabited continent. Interestingly, dragon myths evolved independently in Asia and Europe. How is this possible and what explains so many ancient dragon myths? There are two main theories:

1. Real-life creatures inspired the myths. Ancient discovery of dinosaur fossilized skeletons  are an obvious explanation. Another possibility is finding fossilized skeletons of large whales on land (where oceans used to exist) could have inspired dragon myths.
2. The human brain: Anthropologist  David E. Jones believes that belief in dragons arose out of our innate fear of predators and this fear of large predators gave rise to dragons in ancient folklore.

It seems reasonable that a combination of these factors caused the rise of dragon myths in out ancestors.