4500-5000

Nonetheless, the radiation levels increase, and the insects and other animals continue to evolve, but at a much different rate than before.  They eventually mutate into the monsters first seen in Monsters University, and immediately reset society also, building a version of the world the humans once lived in.  But the creatures soon wipe out the very few humans still left on Earth, and in precaution of preserving their own species, the monsters teach their young that the humans are from another dimension, and are deathly toxic.