Why do all cultures have dragon myths?

I've long wondered about where the ideas for our mythical creatures came from, especially ubiquitous ones like the dragon:

Of all the hoary old monsters, dragons are the most persistent, appearing everywhere from mall crystal shops to Disney movies. Cryptozoologists search for its cousins, the Loch Ness monster and the mokele-mbembe of the Congo swamps.

Dragon images have been found on the Ishtar Gate of Babylon, on scrolls from China, in Egyptian hieroglyphs and Ethiopian sketches, on the prows of Viking ships, in bas relief on Aztec temples, on cliffs above the Mississippi River and even on bones carved by Inuits in climates where no reptile could live.

Now scholars drawing on primitive art, fossilized bones and ancient legends are struggling to explain how cultures that had no contact with one another constructed mythical creatures so remarkably similar. And why did dragons persist so long?
...
In ''An Instinct for Dragons'' (Routledge, 2000), Dr. David E. Jones, a professor of anthropology at the University of Central Florida in Orlando, posits a biological explanation that jibes with the Jungian notion of unconscious collective fears. He argues that the dragon image, fermented in the primal soup of man's first nightmares, is a composite of the carnivores who fed on human ancestors when they were tree-dwelling monkeys: the pythons, the big cats and the raptors.

Whole article here.