Boredom

One day, some trillion years ago, the animal deities got bored.

After conferencing, they determined that the source of their boredom was that their respective creatures had few to no thoughts, so they decided to make a new one. A human.

They tried several times, but none of their creations could think and feel as they could. One after another, creatures made in their image failed to pass a simple test: could they show compassion?

After some time, the animal deities concluded that the being they sought to create could not be made in their images, or it would reflect what already existed too clearly, as they could not imagine an abstract quality into a concrete shape. Once again, they discussed and debated and argued, until the monkey god came up with a series of shocking ideas: what if they created a being with little to no fur or feathers? What if this creature walked on two feet, not four, without wings? When questioned, the deity admitted that he had simply been thinking of things that did not exist.

The deities considered this. Yes, they decided, that would work. But whose species to use as the base? In this, no discussion was necessary: the unanimous answer was that the monkey god's descendants should serve the monkey god's idea.

Surprisingly, it worked...

...and some trillion years later, the animal deities are still regretting creating humans.