Earth's history in The Good Dinosaur appears to be different than in the rest of the Pixar films. (The dinosaurs, for one.) If it is in the same universe, then what happened to the dinosaurs? How does The Good Dinosaur fit into the Pixar theory? While I would prefer a WoG answer from Jon Negroni, any explanation would suffice.
From Jon Negroni:
Pixar Theory author Jon Negroni posted The Pixar Theory, Part 3: ‘The Good Dinosaur’ on December 3, 2015.
The Good Dinosaur hammers the point that when left to their own devices, animals can become just as intelligent as humans, as we also see in A Bug’s Life with Flik’s inventions and ingenuity ensuring the survival of his entire community.
every dino is obsessed with survival [...] There’s not much food around [...] If dinosaurs have been evolving for millions of years, then why are they having such a hard time, now? In the opening scene, there are many dinosaurs all eating together without a care in the world, so something big had to happen between those good times and the bleak world we’re introduced to countless years later.
Well, I think it’s pretty simple. These dinosaurs are living in a “post-apocalypse” of their own civilization. At one point, they probably had plentiful resources to sustain a massive population, much like you’d expect. But what we see is a shifted environment. The lush jungles filled with edible plants that we know existed millions of years ago have vanished by the time we meet Arlo, just as they would have if the asteroid had hit Earth.[...]
mammals (AKA humans) are stealing their food and thriving in this new environment[...]
These storms are a product of this change, as the world gradually corrects the imbalance of reptiles and mammals caused by the lack of an extinction-level event.
And many years later, the same “correction” will happen between man and another new species: machine. [...]
If The Good Dinosaur exists in the same timeline as movies like The Incredibles and Finding Nemo, then where’s the evidence of those movies being a result of this alternate universe where dinosaurs ruled the Earth much longer than planned?
What about fossils? Certainly, the Pixar movies would exist in a world where the fossil record is drastically different. What about these strange creatures in The Good Dinosaur that don’t look like any animals we’re aware of, like the dreaded cluckers?
Well, that’s where Up comes in.
It’s no dinosaur. It’s a bird (Kevin). And this is a bird that bears resemblance to the bizarre makeup of the “prehistoric” birds and raptor-hybrids we see in The Good Dinosaur, who have originated from this alternate universe where evolution was never halted. [...]
So Kevin’s existence, as well as this rare, superhuman ability, finally has an explanation. Somehow, the longer evolution of these strange creatures brought about magic — or at least something that resembles magic — that can eventually be harnessed by humans in various ways. After all, what is it really that makes those dogs in Up talk? And is it any surprise that Muntz comes across Kevin’s existence in the 1930s, not long before the sudden rise of supers with strange abilities? [...]
Remember: The Incredibles takes place in an alternate version of the 1950s and 60s. Mr. Incredible was very young or even born around the same time Charles Muntz was uncovering what could be “magic” properties. This could even serve as an explanation for why academia suddenly turned on Muntz, shaming him for what we know weren’t fraudulent discoveries. Perhaps this was a ploy to keep his research hidden from the world, explaining why only Americans are shown to have powers in The Incredibles. [...]
OK, what about the strange animals mentioned earlier? Well, when we explore the dirigible in Up, Muntz shows off his collection of these strange creatures that are so rare, Muntz doesn’t expect Carl to know what they are.
They range from giant turtles and other aquatic life to hybrid mammal/dinosaurs that are reminiscent of Forrest from The Good Dinosaur. And we can now deduce that in the Pixar Universe, many of these creatures existed closer together in time, explaining why they’re displayed as a group. [...]
So the exotic creatures from The Good Dinosaur apparently exist across multiple Pixar movies, and the absence of an extinction-level event seemingly provides an explanation for why animals have become so intelligent by the time we get to movies like Ratatouille. And the movie even provides some hints as to why magic exists in the Pixar Universe, and we now know why said universe is alternate to our own. [...]
In Cars 2, the sentient cars are running out of oil, entirely. And this makes sense for two major reasons:
Mankind has a 200 billion population by 2105 (according to WALL-E) There’s less oil on Earth because (whoops!) dinosaurs died out more gradually. [...]
The absence of other energy options like fossil fuels might provide an explanation for why human energy is so important in the Pixar Universe.
Last year, Pixar's Jay Ward laughed off the theory to Jalopnik saying, "I think somebody had a lot of time on their hands."
"The movies were sort of made in a different order by different directors in different times, in different places," he added. "It's cool that it all worked out that way, but it probably was not intentional."
Recently, Movies.com caught up with "Monsters University" director Dan Scanlon and producer Kori Rae to ask once and for all what Pixar thinks of the very complex universe.
"It's a funny idea, but we would've had to be insane geniuses to have plotted that out." Rae said, "It's nothing that we talk about at Pixar, I don't think. Or at least I don't. I'm sure people do, though."
So, while the theory is fun and in-depth, it's definitely no more than that, a theory.
SuperCarlinBros speculate on this in their video "How The Good Dinosaur fits into The Pixar Theory":