, Please 
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...but I suppose I have found something which might be (one of the?) origin(s) of the myth of fire-breathing dragons: It's a reptile living on an island somewhere around Indonesia, it's called the "Komodo dragon" [it's mentioned in John Perkins' "Confessions of an Economic Hitman" somewhere in the first chapters when he describes how he prepared for a job in Indonesia] and I've read about it before under the german name "Komodo-Waran" [in Douglas Adams' "Die Letzten ihrer Art" ("The last of their kind"), a report on his journeys to some animals close to extinction in the 1980's]:
It is about 2 meters long and half a man high [that's a little less than a meter, I guess] and lived, originally, on indonesian islands but nowadays survives on only one island. Its mouth "smells like no other creature [Adams] know[s], you can smell it fifty meters against the wind" and its saliva contains bacteria as dangerous to anything alive as not many other things. A story quoted by Adams: Some french adventurer in the 18th century got bitten by one of these creatures and survived the journey back to Paris but died a couple of months later because the wound simply refused to heal...
...and now go and figure out what kind of stories earlier people would tell about something like this and consider these factors: a) people like to adjust facts to make their stories more interesting [well ... people who hear this story might adjust them as well] and
most stories where told from generation to generation since there was about no written history. This has to lead to speculations about mythical creatures...--note: I am aware of the fact that this attempt to explain some myths is not going to give a satisfying explanation when you ask about the origin of dragons in, for example, the german tales of heroes [I'm using these tales as a reference because I am not firm in the tales of other countries. The german tales of heroes are set somewhen between 600 and 1200AD...]
