Actually, if it's the same show I watched recently, then the conclusion was not that dragons existed but that ancient people mistook the world-wide finds of dinosaur fossils as evidence of dragons. Most prevalent dragon myths? China. Largest source of dinosaur fossils out in the open? China. QED.

In much the same way as evidence begins to suggest that Greek myths of an "age of heros" in which the people were much larger than life and things such as cyclops existed can be directly related to the frequent unearthing of mastodon fossils and such in the Greek Isles.