Life began 3.5 to 4 billion years before the events noted in these stories took place on humanity's original homeworld. Starting as single-celled organisms, these simple organisms began to evolve over long periods into multi-cell organisms and then into more complex life forms. Evidence of human evolution began approximately 4 million years ago.
After the move to Damia, the original home world was increasingly called Terra or Sol-3, referencing its position among the other satellites orbiting around its sun.