" By Gold’s model, the intraterrestrials—the oxygen-allergic, heat-loving, rock-eating darkness-lovers—were not a mysterious offshoot of us surface-dwellers. They came first: we were the offshoot of them. With that, Gold submitted an entirely new scene in our creation story: after millions of years gestating down inside the warm earth, a cluster of archaic microbes split off from the rest of the underworld inhabitants and slowly migrated upward, until they emerged into the light, where they gradually began to propagate aboveground. “Microbe pioneers,” Gold wrote, “invaded the surface from below. "

― Will Hunt , Underground: A Human History of the Worlds Beneath Our Feet