Earth's animals were never evolved to kill humansFirst of all, that's completely ridiculous. Second, the animals don't even act that way during the movie. Third, it's possible that over time, during humanity's stay on that other new planet, Earth's inhospitable nature and the circumstances of mankind's subsequent migration to space were exaggerated either by people who wanted an exciting story or people who wanted Mother Nature to seem like the bad guy. Now, everyone just thinks that everything on Earth has no desires beyond extinction of humanity, when they're really just... acting like ordinary animals.
Rangers were genetically engineered from Autistics.The difficulty they had expressing emotion caused me to think of this. It was mentioned that the Rangers were originally leading humanity in its exodus from Earth before the Ursas came. At this time they weren't warriors, they were just leaders. They'd been created when humans realized that it was their inability to put aside their emotions that had caused the destruction of Earth (ie thinking in the short-term, and looking for gratification over sustainability), so they had to create a new breed of humans who could put their emotions to the side. Now, Autistics today aren't really like this, but the genes that make them more socially awkward are still (in this movie's verse) usable to make people who are just generally less emotional. When the Ursas attack, they're able to use this to wildly decrease their fear responses, and eventually to Ghost.
- Autistics have trouble with facial expressions, not pheromones. And we feel the basic emotions, fear, rage, sorrow, happiness, at the same strength as neurotypicals, if not more. It's complex emotions like jealousy that we have trouble with. In addition theautistic meltdown phenomenon makes autistics tend to act more like Berserkers in a fight than the calm, collected warrior that Rangers act like.
- It's more likely they came from schizoid personality disorder, which features a flat emotional range due to withdrawing into the mind and blocking out other relationships.
- Or it could simply be intense self-discipline training.
After Earth exists in the same universe as Life After PeopleHumans didn't disappear, they just spontaneously left. Several thousand years later, the events of this film occur.
After Earth is the sequel to The Happening.Cypher says that every animal on Earth has evolved to hunt and kill humans. We can assume from the Happening that the biosphere was turning against the humans, and the plants emitting a suicide gas was only the first step, and soon animals and the weather started turning against humans as well, forcing them to leave the Earth. The re-breathers that Kitai Raige takes periodically contain something to prevent the plant's suicide gas from affecting him.
- That could explain the way the plants moved when it's about to become cold.
After Earth is the future of The Hunger Games universe.Think about it: the Ursa were originally one of the genetically engineered tests in the arena — the next step up from the Muttations and the tracker-jackers. Panem decided to use them as a weapon against an enemy state, and they got out of control and devastated humanity. Same with the weather - it's an experiment Gone Horribly Wrong.
- I like that. It'd be very like Panem to say "uh... those must be aliens attacking, because why would we make THAT?".
After Earth is the sequel to The Day After TomorrowBecause we messed up the weather and the "fast freeze" now happens every night.
After Earth is the far future of Zoo.Hence, the giant animals inexplicably adapted to kill humans, whose rampages eventually drove humanity off the planet. No, it doesn't make much sense in Zoo either, but at least it'd be consistent.
It's not Earth.It was just a bad terraforming attempt, or one the aliens made go sour. But the point is they're mistaken about that particular planet being Earth.
Earth's animals were genetically-engineered as part of the environmental cataclysm.The film doesn't really give specifics on how the Earth came to be uninhabitable, so for all we know, mass genetic engineering could have played a part in Earth's downfall, which would explain how quickly and radically Earth's biosphere evolved.
Earth hasn't changed at all; humans have.After civilization collapsed and humanity fled into space, they genetically altered themselves to adjust to life on space stations and the world they colonized. Adapting themselves to life in the cramped, artificial environment of space habitats required them to shrink down to about three feet high - hence, the (perfectly normal) baboons, eagle and wild cats look huge next to Kitai - and settling on a new world meant altering their physiology to fit its atmosphere, not Earth's. The reason Cypher claimed that Earth's animals were "evolved to kill humans" is because our reduced proportions placed us into the size-bracket of "appropriate prey" for a whole lot of predators that would leave a full-sized present-day human alone.