From the introduction:
Ten thousand years ago, humanity abandoned earth. Ten thousand years ago, humanity destroyed its homeworld. Ten thousand years ago, the Sav banded together after the collapse of the governments and built the Arhat. The Arhat, a massive multigenerational starship, gathered together remnants of the human population, earth animals, and planet, and then set out across the stars. With them, they towed one end of a joined singularity. The other end sat anchored among the gravitational pull of Sol.