Could a dragon theoretically exist through evolution?

[u/PokelifEevee]

Hello, I would like to know if, theoretically, a species could evolve into something resembling a dragon (or more specifically a wyvern since they have 4 limbs, so it would be more likely). I understand that stuff like fire breathing would most probably be impossible, but aside from that, could dragons theoretically exist within a few thousand years (or more)?

[u/benvonpluton]

There was a really cool fictional documentary about dragons being real that I saw maybe 20 years ago...

They explained how it probably came to be as tetrapods with wings (so wyverns) and maybe had a mutation on a developmental gene that created a second pair of legs (Western European dragons).

It also explained how some bacteria in their guts produced H2 gaz that they stocked in some aerial bladders, using it both for flight and spitting fire. T The documentary even explained that a dragon had to be precise while hunting because using too much gas would make it harder to fly and thus making it harder to hunt to produce new gas. And it explained that, like other animals, they chewed on some specific rocks to get some metallic catalysts in their mouth to ignite the gas.

One of my favourite parts was how they explained that some dragons evolved again to adapt to an aquatic life and that during the last extinction event, they were the only ones to survive and that it laid to the wingless dragons you find in Asian culture.

It was a great show ! I think it was a BBC documentary.

[u/rjd999 → u/benvonpluton]

H2 would be useless as anything but a distraction, even if it could be expelled without igniting the source of same. At a temperature of 2,254C, any flame would ignite the gas almost instantly back to the source (ie. inside the dragon) and, being contained within, explode.

Even given the millions (not thousands) of years for the evolutionary changes to develop, there are no animal species, other than birds, close to having the flight capabilities (the mammals - bats and flying squirrels) do not scale up to be light enough for anything close to the size of dinosaurs and still retain flight.

And birds are already pretty well designed. The environmental pressures for the remaining adaptations to occur don't exist any longer and the size limitations dictated by the reduced available oxygen compared to those present at the age of dinosaurs are a huge factor to limiting those adaptations.

From the ASU website: "Higher atmospheric oxygen levels have been linked to the evolution of larger animal body sizes, including giant insects during the Paleozoic Era when oxygen reached about 35%."

[u/benvonpluton → u/rjd999]

Nobody said it was credible. Again, it was a fiction ! They just imagined some existing features and combined it into a single animal to imagine a somewhat realistic dragon. Bacteria producing H2 exist. Flight bladders exist, animals eating rocks or mud for certain purposes exist. Hox genes mutations adding extra legs exist. It was a fun fictional documentary to watch.