Europeans. The precursor to Caucasian dragon mythology were giant snakes which appear everywhere in their folklore, sometimes with two legs. Eventually they were given a full four and a pair of wings. Orms, Dragons, Sea serpents, serpents.... it's all the same origin.
Everywhere the Indo-European peoples went in their expansion, they seem to have brought along stories involving giant snakes. Often this shows up in the Chaoskampf storm god myth, which is introduced in many different forms including Leviathan (Tiamat) in the bible being smote by god. And this is not just a regional thing limited to a few areas: it's practically all of Europe, from the British Isles to Norway to Germany, to possibly even France and parts of southern europe.