> You'd then have two environments where life could evolve completely independently. Earth definitely has places where evolution happened in a more-or-less iso

> You'd then have two environments where life could evolve completely independently. Earth definitely has places where evolution happened in a more-or-less isolated environment for a long time, though probably not from "zero". For example Movile Cave: Life in the cave has been separated from the outside for the past 5.5 million years and it is based completely on chemosynthesis rather than photosynthesis. https://en.wikipedia.org/wiki/Movile_Cave https://en.wikipedia.org/wiki/Movile_Cave Look up pictures from that cave at your own risk. Personally I think those critters are the stuff of nightmares. I don't doubt there's an uncountable amount of ecosystems on Earth we haven't even found, much less understood. We (literally) have hardly scratched the surface of this planet.