Long ago existed a race known as humans, they were a strange species and the first sapient mammal that took dominion of Earth. They made many great things, but also many horrible things. The humans enslaves and modified many species to work and live for and with them. Though after the thousands of years being alive the humans began to completely change their behavior. Most of them started to become wiser and care more for nature and experimentation. All the human nations combined into one Planetary Empire and the humans that didn't agree with the ideologies of the Human Empire were banished to live in the many wilds that were abandoned. To never be seen again by the Empire humans. Then strangely they began to modify some of their slaves and many of the wild creatures, even creating new creatures that carried the mental values of the human animals. They took furry beasts that climbed in trees and swam and lakes, large two-legged animals that walked on their knuckles, they made creatures out of their own blood and "souls". They cared for these creatures and put each creature in a habitat with the hopes that they would become the dominant species of that region. The humans visited their creations for many years and years, until they never returned.
Many species were founded by humans, some of these species were taken from non-sapient animals, while other were "created from scratch" using genetic material of humans and maybe some other animals. Many of these species at least known something similar to humans, whether it be language, physical attributes or to a degree basis for culture. Nearly all sapient species are bipeds that are Trichromacy with FOXp2 genes comparable to humans. This is largely because of human beings wanting to have a closer physical relationship with their creations so communication and many other things were possible or at least easier to establish.