If that was the case why would the knowledge not be passed down? Why has it taken so long for us to develop technology etc?what if "we" came from somewhere else as non-corporeal beings and discovered life here and chose to 'inhabit' whatever the species before 'the missing link' was...
Again assuming bona fide ETs are hanging around, it's my thinking that we're being protected by ET environmentalists. Would not we have a "look but dont touch" attitude in the reverse scenario?
And what reason would any ETs have for dropping in and saying "here we are"? We'd be like give me give me give me, because we have nothing to offer.