Lore

The precursors were an extinct species that lived so long ago that every species that has lived since thinks they are ancient, so nobody knows much about them. The only thing left of their time are the totems, Terminus, and the Aether.

The Totems
The totems are gateways to dimensions of strange matter/energy that can be harnessed to do basically whatever you want. They were built by the precursors, which, along with many other species throughout history, eventually realized that the totems are sort of a great filter that kills off 99.9% of all species that harness it. When a sapient species touches one of the totems, a small gateway is created temporarily to the respected dimension, and some of the energy leaks through. This energy will sometimes crystallize into shards, which are essentially one-time batteries of the dimension's power

Humanity
Humanity also fell victim to the great filter, but it happened much slower due to their chaotic nature. They had enough time to recreate a distant evolutionary ancestor to humanity, packed thousands of them into stasis inside a colony ship, and then sent them off to the least populated arm of the galaxy. They hoped that their project would remain unaware of the totems and live to evolve humanity once again from the stone age. They evolved pretty much the same since the planet that was chosen largely resembled earth. The player and the NPCs are a part of this neo-human species (excluding Gim and Jim, which are non-sentient androids created by the neo-humans).

Original Solar System
All of the humans left on earth after a mass exodus (to escape pollution) went insane like 99% of humanity, so earth was slowly reclaimed by life after a course of a million years. Mars was terraformed at some point and didn't have the same pollution issues, but the great filter still killed out everyone on Mars