Disastrous accident

800 million years ago, earth was a wasteland. Only bacterial life, sponges near warm water reefs and some ... The oxygen levels were low.
The AI decided that this was an excellent place to begin terraforming. and so it did.

A tiny accident

Terraforming takes long times and Atlantis is a shielded environment to prevent uncontrolled effects. There are no living things on Atlantis. Replicators create all kinds of things, from the basic DNA to a full plant or animal. Later, when a seal breach occurred, the seal repaired itself but... The seal blows a few small fungi and some spores out. As incident its tiny. But on this pristine world, this unnoticeable little detail will spell disaster. In the eons that followed, some tiny things happen. A small patch of green occurs near the border of the AI.

100 milion year later

Lush green fields surround the AI. some bushes can be seen

200 million year later...

Large forests surround the AI. Some trees are over 100 meters tall. They are huge. clouds are forming

270 million year later…

The oxygen released by the plant life creates clouds, the clouds block the warmth of the sun and that in effect has as effect that the temperature goes down significantly.

30 million years pass

The world is getting colder and colder The world encapsulated in ice (snowball earth) are clear signs that the terraforming formula has failed. big time. Aivitu has a tough decision to make. He calculates, and the outcome is very unfavorable and moves to another planet in our solar system.

what has happened?

Right now there’s not enough information to decide whether animals created Snowball Earth, or Snowball Earth triggered animal evolution. But either way, it links the two events.
The fungi and spores developed into pockets of microscopic plants, which released oxygen as a waste product. the pockets became more and more as the fungi spread and that delivered more oxygen to the planet. The oxygen levels had a second effect ... the earth would create a blanket of warmth blocking clouds. lowering the temperature globally significant.