The theory that planets, planetary systems, and galactic regions that facilitate the development of complex life as Earth does are rare. This does not rule out microbes and the like, but anything else according to this theory is unlikely.
Game and Story Use
- If Earth-like planets are rare and complex life can only originate from Earth-like planets, then that gives humanity a special place in the universe; it is up to us to spread life throughout the cosmos, that it may not die out with us. If we don't do it, there's a good chance no one will.
- The seeded life may well come to regard us as Precursors if and when it reaches sapience. Three questions arise from such a situation: are we benevolent, neglectful, or abusive and are we alive or dead by time they reach beyond their homeworlds?