Where did the idea of dragons come from?

The mythic concept of dragons originated so far back in human prehistory that any answer we give will be speculative. One hypothesis suggests that "accounts of spitting cobras may be the origin of the myths of fire-breathing dragons." It is of interest that the oldest evidence of religious activity is a 70,000 year old cave shrine in southern Africa containing "an elongated rock, carved to enhance its resemblance to a snake." [2] It's not a big conceptual leap to go from a giant spitting snake to a fire breathing dragon. Just add legs. :)

I'm not so sure that dinosaur bones were the primary motivating force behind the origin of the dragon myth. Of course, ancient peoples digging wells or foundations for buildings did occasionally stumble upon them. However, they didn't have the scientific knowledge to reconstruct the animal to which the bones once belonged, let alone recognize them as belonging to an extinct reptile. It's just as likely (and perhaps more so) that someone who discovered a giant dinosaur femur would have attributed it to an extinct race of human-like giants, such as the Titans of Greek myth or the Nephilim of Hebrew myth, or any other mythical creature in which the discoverer happened to believe. Granted, once the dragon myth had become established, some fossils could be interpreted as dragon bones.

5000 years before Troy the Chinese had already found the huge fossil bones and made pictures and statues of Dragons from the bones.

Odd is the fact that every Coulter has some version even when many had never heard of each other. I would guess dino bones

Maybe reptiles

Dinosaur bones.