Story where most of humanity was moved from Earth to two other planets

Question

There's a story where humanity is an experiment of a robot intelligence from outer space (maybe from the center of the Galaxy, I'm not sure), I'd read this around 7-10 years ago. Said intelligence some day moves most of humanity to two other planets, where warlike civilizations emerge (they also try to reclaim the Earth at some point in the book). Those left behind develop ability to space travel without tools or anything (and, if memory serves, become immortal or very long-lived). There's also a group of Christian robots that've taken humanity's mantle of believing in God. The book ends with one of the believer robots having faith crisis over the aforementioned intelligence.

The author compares at some point humanity to a bacteria strain that was moved from one Petri dish to another - the main population keeps its properties, the leftovers mutate into something else.

The book itself didn't appear either too worn-out or freshly printed, so I'd estimate 80-s as printing period.

Answer 1

After more research, I think this could be Clifford D. Simak's Choice of Gods. It was first published in 1972, but new editions are periodically released.

One day most of humankind disappeared. A few human beings were left on the deserted earth along with countless robots. The human beings--including a small tribe of American Indians--made do. The Indians returned to ancient tribal ways, the others stubbornly tried to rebuild technology. The robots--some stayed with the humans performing their service functions, some went off to create a religiously-based society of their own.

Millennia later, a star-traveler returns from the center of the universe. The people of earth had been found and were planning to return. But something else had been found, too--the central intelligence of the universe!

You have Christian robots, transcendent humans, and a central intelligence.