WMG / The Croods

This film takes place in the same universe as The Flintstones, but centuries earlier.
There are no man-made cities, domesticated or enslaved animals, or advanced culture when this movie begins. All cavemen live like... actual cavemen, with just a cave to live in, no inventions, and simple animal hides for clothing. When Guy comes with an evolved brain and tons of inventions, he inspires the Croods to adopt some of that too, and at the end, they become the first explorers in human history. Guy leads them in finding more Cro Magnums and other cavemen in other regions. Eventually their descendants start Bedrock, and their culture gradually develops. Of course, this begs the question of why dinosaurs exist in Bedrock, and they do not in The Croods.
  • They're just hiding.
  • Dinosaurs live in another part of the world. Earth is big, some parts are inhabited by Mix-and-Match Critters like in this movie, and some parts have dinosaurs like in The Flintstones.

This movie is more proof that The Flintstones takes place in the post-apocalyptic future of The Jetsons.
The supposed Cro-Magnons were actually just the first people to re-discover the Lost Technology and start rebuilding human society, as well as reintroduce and redomesticate the Jurassic Park-style clones of dinosaurs and other prehistoric animals (although some cloned sabertooth cats and other Pleistocine animals obviously escaped and interacted with the Croods and their compatriots). The Croods and their kinfolk probably just lived in a different part of the world and the proto-Flintstones merely acted as technological "missionaries".

Alternatively, 'The Croods could take place after The Flintstones. The Bedrockites were rebuilding human society in chronological order; hence why characters in The Flintstones acted like 1960's Americans while the Crood family acted like people of The New '10s ("shell phones" and all).

Eep and Guy are Cro's Parents
For those not in the know, Cro is an animated science show from the early 90's.

Orphaned Cro-Magnon is adopted by Neanderthals whose patriarch is against new ideas.This could refer to either. And Cro has red hair, is exceptionally smart, and doesn't bat an eye at highly intelligent creatures.

The story isn't set on Earth at all.
The vast majority of the film's flora and fauna are far, far too different to have ever existed on our own Earth. Rather, the characters are descendants of a failed space colony on an alien world. The Croods' ancestors were future Super Soldiers, genetically engineered to be strong, fast, and fierce, while Guy is descended from unmodified humans. These two branches of humanity went their separate ways after the colony failed, and the Super Soldiers forgot even more of their former technology than their unmodified counterparts. Only their shared language and a few rudimentary concepts (e.g. that stars are suns) survived the passage of generations.

The Croods and Guy are different species of human.
The vast majority of the Croods strongly resemble Homo neanderthalis, while Guy is almost certainly Homo sapiens given his appearance and behaviour. Since the two existed at the same time and could interbreed, it's not impossible. In addition, Ugga is half-sapiens - she looks a lot less Neanderthal than Grug or Nanna, while Sandy and Eep look slightly sapiens.

Guy is a time traveller from the future.
He seems to know much more than the Croods, and even though the majority of that must be because he's actually been outside a cave in his life, there are just some things that don't make sense, like knowing the names of several things that just didn't exist yet or couldn't be named yet.
  • I believe the implication was that he was the one who named them. Or that it's simply being translated for our benefit, considering I doubt they spoke English in XXXXXXXX BC.

This film is set not in the past, but actually in the distant future.
Look at the animals in this film. There is no possible way this could have taken place in the past. This is clearly a post-apocalyptic future where humans have become an endangered species. (Kind of like After Man: A Zoology of the Future, or The Future Is Wild.)

The Croods themselves are possibly regular humans who reverted back to a caveman-like state. Most of them have an instinctive fear of anything "new", due to subconscious memories of how humans have junked up the earth in the past. Guy is one of the last remaining "regular" humans.

Every single creature in this evolved from a modern-day animal.
  • The Macawnivore evolved from feral domestic cats. The strange color is for camouflage purposes.
  • The Turkey Fish evolved from a group of duck species known as Mergansers. The "teeth" are actually developed versions of the bill serrations their ancestors had.
  • The Bear Owl evolved from some kind of mustelid.
  • The Liyotes evolved from frilled-necked lizards. The "fur" is actually a feather-like substance similar to what some dinosaurs had. The "nose" is just a colored patch of skin at the end of their snout. And the "ears" are just the flaps that their ancestors had, only smaller. Their ability to run on their hind legs is similar to what their ancestors had, but have become more efficent at it.
  • The Ramu evolved from tinamous. The "horns" on its head are a keritinous substance similar to what rhinos have, albeit with feathers instead of fur.
  • The Crocopup (AKA Douglas) evolved from some kind of small carnivore, possibly shrews or weasels. The reptilian head is a case of convergent evolution.
  • The Girelephant evolved from a small group of elephants that were being held for conservation purposes, but later escaped and formed a wild population. Its spots are for camouflage.
  • The Trip Gerbils could have evolved from some rodent. Every single pair of young is born with a conjoined tail, but I'm not sure of the implications of two individuals sharing blood.
  • The Mousephant most likely evolved from (what else?) Elephant shrews.
  • The Piranhakeet probably evolved from a small, carnivorous songbird that eventually started hunting in flocks, which allowed them to hunt small prey.
  • The Jackrobat might be a regular bat species that developed rabbit feet so it could run better while on the ground.
  • The Turtle Doves evolved from some kind of herbivious bird species, possibly macaws. The developed four wings, similar to Microraptor and spends almost all its life in the air, just like swifts. The shell could have been developed out of hardened feathers, but is very light, so that the bird can fly easily.
  • The Ground Whales developed from a small species of baleen whale. This species was forced to move onto land due to water getting shallower, and had to redevelop legs.

The Croods is the prehistory of the world of Avatar: The Last Airbender
Hence all the mix and match critters.

The universe depicted in the movie is not our prehistoric times (obviously), but that of a fantasy world.
Would explain why the animals are so bizarre. We just don't see the resulting fantasy world because the movie is set only in that universe's prehistoric times.

The Croods and Guy will find other survivors of The End in the sequel or TV show
With the announcement that there will be a The Croods 2 and a TV show, the potential to run into other Neanderthals and Cro-magnons is likely, with potentially their own customs and cultures. Among those other survivors, there'll be the former neighbors who were taken away by the giant fly. Unlike the other lost neighbors, they were never seen being killed. After escaping the fly, they had no idea of how to return and eventually decided that wherever they are now is better anyway.