Has anyone yet discovered a living, possible "missing link", between Homo Sapiens and the rest of the great Apes ?
Besides causing a huge philosophical debate (creation, religion, evolution etc), and considering how staggering of a discovery it would be, I'd say any of the other species or sub-species discoveries you could mention from the last several hundred years, would pale in comparison to this.
This discovery would be a game changer, and there is no way to estimate just how explosive of an impact it could make.
For that reason alone, there exits reason to believe that there are people, entities, and organizations (Govt or Private), that would want to suppress such a discovery.
Same goes with possible ET / UFO activity...
Art