I've never seen gravity demonstrated definitively either. Sure, they say that there's this force that makes stuff fall, but I've seen plenty of things go up instead of down when released.
That is farcical. If something is thrown in the air, you can demonstrate the force of Newton's constant, thereby definitively demonstrating gravity. Actually calculating the gravitational constant with precision is the only difficulty there. Nothing about this is assumed. Which back to the point, is nothing like the assumptions of hereditary lines in the so-called "fossil record".
