Why do humans exist? Well, *someone* has to be the apex predator!
Humans exist because the Gestalt knew that momma Gaia would be getting cool so something had to exist to make SUVs to warm her up.
Oh, and something was going to be needed to take care of domesticated pets.
So, the Gestalt decided to score a towfer and get both issues solved with a single device. That device is humans.