Quote:
Originally Posted by scc
But from the look of things there might be a few problems with that. While Bacteria, fungi and other single celled lifeforms. But what about slightly bigger lifeforms, could plant seeds have made interplanetary or borderline interstellar trips clinging to the side of a meteorite?
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One solution to this is to simply decide that there's an unknown mechanism by which certain patterns of evolution repeat themselves.
e.g. on every planet, some strands of the original extremophile bacteria (that have seeded so many planets) tend to evolve into photosynthetic plant life--whenever that happens, animals evolve to take advantage of the oxygen surplus and the potential food source represented by the autotrophs.
This is hand-wavy, of course, and ignores the random nature of natural selection, but it would explain why there's edible plant life where ever you go without having to posit seeds that survive the trip through space.
I would even suggest that the extremophile bacteria (likely the first life-form) evolved on a comet, and was spread to other comets and planets by collisions.