Martians were the dominant species of Mars in a universe riddled with overlapping timelines.
Many versions of the human Jack Kowaczski travelled back in time to Mars in an attempt to warn the Martians that they would be enslaved by humans during the 20th century. All of these incarnations of Jack died on the hostile surface of Mars and their corpses decayed, releasing water and nutrients and changing the Martian environment so that it could support life. The gut bacteria from the dead Jacks evolved over millions of years into insectoid Martians who were enslaved by humanity, and thus inspired the Jacks to travel back in time to try and warn them to protect themselves. The Martians then travelled back in time to prehistoric Earth and culled the early humans using robotic machines. Occasionally, they would take a human and make them into one of their own to preserve the species. (PROSE: The Last Resort)