Giraffes

Giraffes are mammal animals originating from Earth. By the year 3000, tiny specimens had become pets for Humans. In the year 1,000,000, when the planet will be medieval again, they will become sentient creatures and enslave Humanity. The length of their reign is unknown, but it can be assumed it will end when Humans either fight for their freedom or until they evolve into the intellectually and morally advanced creatures and the Dumblocks by the year 5,000,000.