Dear 100 Hour Board,
How similar would extraterrestrial life be to life on Earth? Obviously, other planets would provide different habitats that organisms would have to adapt differently to, but would we still see some of the same common evolutionary mechanisms producing similar kinds of plants and animals? Might there be coniferous forests? Lichen? Eyes and ears? Vertebrates? Fish? Even mammals?
-curious george, wondering if somewhere there's an alien monkey who would be his friend
There is literally no way to know this. Like, we don't even know why evolution turned out the way it did on Earth, or what is ultimately possible. As Frère pointed out, we don't even know if life would have the same molecular structure.