So, if these entities we know as the grays are not from another planet, or perhaps not even aliens after all, then what? The theories and speculations are legion. It has been postulated that primates may have not been the only of earth's species to evolve into intelligent creatures, that the grays may be the end result of the evolvement of dolphins, turtles, whales, insects, or dinosaurs-and that these evolved forms may be either terrestrially or non-terrestrially oriented.
Lots of good stuff here.
(Thanks again, Steve!)