10000

In-universe

 * Earth is an post-apocalyptic wasteland, and humans have become technologically simple folk. There are monuments indicating that since 3010, Earth had been ruled by apes, birds, cows, and some slug-like creatures, in that order.

Trivia
The idea of the different species taking over (as well as their versions of the [Statue of Liberty] remaining is a reference to [Planet of the Apes]