We might just not in our lifetime or our childrens or their childrens etc. I love thinking of this stuff, just not all the time, or my head would be so sore.
The chicken or the egg, its more of case that, What came first, cells or multi-cell?
But i was reading more about this and something i read made perfect sense, we might not of come from earth after the big-bang but our cells were brought down on Meteries, sounds like BS but think about it, if we did come from another planet then well there is other people or 'aliens' out there.