Unfortunately, I do not think that the characteristics presented, or the evolutionary theory, hold much water on close scrutiny. Key to this is the fact that we ignored on dragon that appears in Tolkien: the Great White Dragon of Roverandom*. With the new description, it becomes clear that only the reptilian aspect of dragons continues to hold merit.
The Great White Dragon lives in the moon and is responsible for eclipses: “Once or twice he had been known to turn the whole moon red, or put it out altogether” (Roverandom chapter 2). However, even when Roverandom and his fellow dog Rover (yes, they are actually their names) wander into the dragon’s cave, there is not even the barest mention of treasure. Perhaps it’s because the protagonist is a puppy, but I don’t think so. The reason for that is, as Tolkien gives the dragon’s history, he at no point gives any indication of treasure.
He [The Great White Dragon] fought the Red Dragon in Caerdragon in Merlin’s time, as you will find in all the more up-to date history books; after which the other dragon was Very Red. Later he did lots more damage in the Three Islands, and went to live on the top of Snowdon for a time. People did not bother to climb up while that lasted—except for one man, and the dragon caught him drinking out of a bottle. That man finished in such a hurry that he left the bottle on the top, and his example has been followed by many people since. A long time since, and not until the dragon had flown off to Gwynfa, some time after King Arthur’s disappearance, at a time when dragons’ tails were esteemed a great delicacy by the Saxon Kings.
This also reveals the Dragon’s flaunting of the second point: there is no hero to oppose the Dragon. While on Earth, only a Red Dragon is strong enough to even fight the White Dragon, and he loses. On the Moon, even the Man in the Moon (a great wizard), was “was a bit bothered by this dragon”. While the Man does rescue the two dogs from the Dragon, he doesn’t kill the dragon, just puts it out of sorts for a bit. This is different from every other dragon except, I would argue, Fafnir. After all, Sigurd simply ambushes Fafnir when he is heading to the river for water. There is no confrontation like Turin and Glaurung or Bilbo and Smaug; Fafnir doesn’t know he had an adversary until he died. Still, the Great White Dragon has no comparable mortal, and it doesn’t make him any less a dragon.
To Tolkien, a Dragon clearly did not require a horde of gold or a hero. Instead, his dragons seem to require devastation. They are dragons because they cause damage, either physical or psychological. This holds true for all of the dragons: Smaug and Beowulf’s wyrm burn villages, Glaurung terrifies the Elves outside of Angband and later sacks Nargothrond, Chrysophylax steals gold from the villagers, Fafnir stole Angvari’s treasure. This is similar to the horde, as that can be the result of the dragon’s rampage; however, the horde is a symptom of a dragon, not a characteristic of it. This also bears some similarities to the interpretation of dragons as natural disasters as well. However, there is a second characteristic that Tolkien gives that differentiates itself from this: the importance of the dragon leaving the lair.
All six dragons do leave their lair**, and it is only by leaving that they can be defeated. When Bilbo meets Smaug in Erebor, Smaug is quite aptly named the “Stupendous”. Even though his weakness is visible, there is no way to act on it. Even in Roverandom, the Great White Dragon is turned aside by a rocket, because he left the lair. The act of devastating is a moment of weakness, unlike a natural disaster. Perhaps, this leaves one important observation left in class: the dragon, as the ultimate monster, is fundamentally unknown. Observing the monster revealed takes away its mystery, degrading it into another beast to be killed.
*Roverandom requires some introduction. It was written by Tolkien in 1925 originally as a story for his sons. The story follows a dog who angers a wizard, and is briefly turned into a toy, before being rescued and going on adventures on the moon, under the sea, and a brief excursion to the Far West of Faerie. Only in the mention of Faerie is Roverandom connected to the Legendarium at all (it theoretically takes place in 1925).
**Technically, in Beowulf, the bard claims that Sigurd killed Fafnir in Fafnir’s lair. But that version of the story is not corroborated in the Nibelungenleid or Volsunga saga, so I disregard it here.
Tolkien, The Silmarillion
Tolkien, Unfinished Tales
Tolkien, J.R.R. Roverandom. London: Harper-Collins, 2013
Heaney, Seamus. Beowulf: A New Verse Translation. New York: Farrar, Straus, and Giroux, 2000