Earth

The Earth in this universe is broken, a remnant of what it once was many, many years ago. Humans destroyed each other with weapons of mass destruction. The humans that survived this traveled the nearby planetary systems until they found Axis. A small terrestrial planet with little atmosphere that they built structures on. Some humans still remain on Earth in the few habitable spots remaining. The similarity of plants between planets leads people to theorize that during the humans spread for a new home, the put plants on all the planets the visited