Gastornis: Well, what about the dinosaurs?
Manny: The dinosaurs got cocky. They made enemies!
Maybe what killed all the dinosaurs wasn't a meteor, or a flood, a drought, or any other sort of geological event that might have happened 65 million years ago. Maybe it wasn't even due to powerful aliens intervening or time-travelers messing around.
No, some writers prefer the theory that the dinosaurs were responsible for their own extinction. They were too stupid to take sensible precautions for their future survival, or were intelligent enough to develop the means of their own destruction. Either way, this provides a lesson for the human race and other sapient species if they want to avoid the same fate, though paleontologists might not believe the story.
- A dinosaur holding the wrong end of the wand when performing his vanishing spell, so they all went to the Land of Lost Things (Donald Duck). Remember kids, improper handling of dangerous equipment grants horrible consequences.
- The Far Side jokes that dinosaurs died out via smoking. This becomes Hilarious in Hindsight when one finds out that the cannabis family (which also includes marijuana) were important ground cover plants in the Mesozoic. Maybe Larson isn't so off the marker after all.
- The Perry Bible Fellowship posits that the dinosaurs chose to go willingly.
- Discussed in Ice Age 2: The Meltdown, in which Manny, who is widely believed to be the last mammoth, claims it's impossible for mammoths to go extinct since they're the biggest animals on Earth. When someone brings up the dinosaurs, he states that "the dinosaurs got cocky, they made enemies". Humorously enough, he says this in response to a question from a Gastornis, which is a type of bird. As in, you know, an actual dinosaur. It's later revealed in Ice Age 3: Dawn of the Dinosaurs that some of the dinosaurs are still around.
- A German quip dating back to at least the late Cold War arms race: "Die Dinosaurier sind ausgestorben, weil sie sich falsch entwickelt haben — zuviel Panzer, zuwenig Hirn." ("The dinosaurs died out because they evolved into the wrong direction — too much armor* , too little brain.")
- There is a joke about a male dinosaur wanting sex from his wife, but she complains about a headache, about periods, about being busy... and so it continues until they go extinct.
- Isaac Asimov's "Day Of The Hunters": The dinosaurs are killed off due to overhunting by an intelligent saurian race...with Frickin Laser Guns! In an afterword, Dr Asimov felt somewhat embarrassed later on because it was one of his early ones and had an exceedingly Anvilicious ending, rather than let the reader draw their own conclusions.
- In the story Hermes of the Ages by Frederick D. Gottfried, sapient coelurosaurs develop biological warfare, which they THOUGHT the effects of their bioweapons would be limited to their own species...it goes horribly, horribly wrong.
- Who Lies Sleeping: the Dinosaur Heritage and the Extinction of Man by Mike Magee. Though the sentient dinosaurs are ultimately wiped out by a nuclear war, they had already wrecked the world beyond reparation via massive pollution, climate change and deforestation to give pastures to their massive herds of ceratopsians and hadrosaurs.
- The German language poem Der Ichthyosaurus by Joseph Victor von Scheffel seems to imply that the dinosaurs (and their Mesozoic contemporaries) went extinct because of too much decadence and lewd behavior.
- Larry Niven: "The dinosaurs became extinct because they didn't have a space program. And if we become extinct because we don't have a space program, it'll serve us right!"
Ennesby: Why do Earth people name their largest spacecraft after craters and comets?
- Paraphrased in Schlock Mercenary 9/8/18 (which is amusing trope-wise, because a later strip shows they did see the asteroid coming... far too late):
Tagon: Lots of people name weapons after scary things.
Ennesby: Nope. "Extinct people don't have space programs."
- The 2001 miniseries of The Lost World combines this with an in-universe instance of Science Marches On, with Professor Summerlee arguing that dinosaurs' size and lethargy prevented them from competing with the smaller, more agile mammals. Given that the series is set in 1911, this would not be an unreasonable view for a respected paleontologist to have.
- A New Yorker cartoon by Donald Reilly has a mother disciplining her daughter in a natural history museum, telling her "They got extinct because they didn't listen to their mommies."
- Surprisingly Played for Drama in the last episode of Dinosaurs. The dinosaurs go extinct due to a chain of events that started with Earl's boss stupidly destroying the breeding grounds of a specific species of bug. The dinosaurs try to fix the damage to the ecosystem, but wind up wiping out all plant life, then plunging the planet into an ice age. As the ice piles up, Earl has to explain to his shivering family why they are all about to die.
Ethyl:note I always knew you'd screw up... I just didn't know how bad.
- In The Adding Machine, the Fixer explains that the dinosaurs, like Mr. Zero, had to go because they were a waste of resources:
Fixer: They literally ate themselves out of existence. I held out for them to the last. They were damned picturesque — but when it came to a question of the nitrate supply, I simply had to yield.