I think that 22b is the original home of humanity.

I think that long ago, there was a conflict similar to the one we see humans fleeing on earth, of humanity at war, destroying their planet and making it uninhabitable, and needing to flee to another world. I think that was Earth.

I think that much in the way that humans on 22b have only a modest amount of the tech they brought with them remaining, something similar happened when they reached Earth the first time, retaining only a small amount of their knowledge, allowing the original knowledge of how to combine silicon and carbon life forms to slip into obscurity and remaining only in Mithraic holy texts.

The humanoid "creatures" that Mother and Father discuss as devolving are the remnants of humanity left on Kepler. The snake/lamprey creature that is Number 7 is a species indigenous to 22b (as demonstrated in the snake-like skeletons everywhere) modified by being spliced with Mother. The DNA for the creature was buried somewhere in her code and her virtual coupling jump-started the gestation of a hybrid life form.