Tolkien clearly wrote that dragons were bred by Morgoth but no one is sure how. Some believe that dragons are embodied Maiar, others believe they are simply beasts who were trained by Morgoth to speak and to think, still others suggest they are "sparks" of Morgoth himself. Another theory is that dragons are crossbred from Balrogs and other such fell beasts created by Morgoth .
Dragons were known to be very intelligent. This has led many to think that the theory which suggests that dragons are merely corrupted beasts is false. For example David Day writes, "The intelligence of Dragons was renowned, as was their love of setting and solving riddles. Dragons . . . were creatures of immense cleverness and knowledge but not of wisdom, for their intelligence had the flaws of vanity, gluttony, greed, deceit and wrath."
- The theory that Dragons were simply beasts physically enhanced by Morgoth, such as corrupted eagles, is a very popular theory, but there are issues with this line of thought. Randall Johnson writes: "Dragons understand many tongues, and they are known for speaking in riddles. Dragons are very intelligent, able to lead armies into battle. Dragons are able to petrify and hypnotize with but a glance of their eyes. Dragons cast spells and curses. Some Dragons breathe fire. These properties and powers are not characteristic of simple beasts".
- The theory that dragons are sparks of the spirit of Melkor has merit. According to this theory, Melkor bred monstrous reptiles and poured a portion of his own spirit into them, giving them semi-independent wills and consciousnesses.
- One theory claims that dragons find their origins in Yavanna's creation; they were born to be part of Arda's ecosystems just as other animals, or were specifically created to serve as guardians who would protect the harmony and peace of nature like the Eagles. These beasts were then later (or even before the spread of their races across Arda) altered and corrupted by the Dark Lord and adopted into his forces. Gigantic reptilian races such as dinosaurs, Megalanias, Titanoboas, and the Fell Beasts might or might not have shared their origins with dragons according to this theory.
- The next theory is that dragons are simply embodied Maiar much like the Balrogs. This theory avoids many of the problems of the previous ideas on draconic origins. According to this theory, dragons are Maiar, ancient spirits in the form of gigantic, serpentine monsters. The fact that Maiar have the ability to take on corporeal forms has been established previously. Melkor's deadly allies, the Balrogs, were Maiar in the raiment of fire and shroud. The Wizards were Maiar in the form of Men or Elves. The problem with this theory is that the Maiar are not a race but an order of angelic (or demonic) beings, created before the world began, and do not procreate one with another.
- The final theory is that dragons are actually descendants of embodied Maiar and beasts (more likely monsters or Nameless Things) much like Ungoliant procreates with spiders. This theory is generally considered to have great strength by Middle-earth experts. Johnson writes: "[this] theory contends that at some point in time, a Maia, according to the bidding of Melkor, assumed a bodily form genetically compatible with an existing reptile. Recall that Sauron himself took the form of a serpent. 'Then Sauron shifted shape, from wolf to serpent, and from monster to his own accustomed form.' (Silmarillion, 212) This serpent-Maia mated with the reptile, procreating the first Dragon, Glaurung. Glaurung then mated either with other existing reptiles or with other serpent-Maiar in order to reproduce. Eventually, the Dragons became a self-sustainable race."
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- ↑ http://thehalloffire.net/forum/viewtopic.php?p=273507&sid=1a9814d96b1a3bb9ad0f2ca3f19d7da0
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- An analysis of different theories Concerning the Origin of Dragons