Yes an apple will fall before even humans existed. It was not invented by humans but is limited to what we understand. Eg: law of gravity of newton and einstein.
What they understand before is that due to mass that objects fall, even before gravity was discovered. The later comes law of gravity with objects of proportional mass and then came the curvature of fabric of space time. We did not invent this laws, this is the result of what we observed so far. If still people and scientist are not satisfied then it ends up as theory, but we may brand it as thoery but in reality its a law or vice versa, we brand it as a law but in reality its not.
If you are questioning how this laws existed, as I mentioned above AFAIk we cannot say at atmost 100% that all laws are really laws, we have to remember we have macroscopic and quantum level. Laws may not apply to the other. I would not want to guess how they existed for the first place, but rather we have to dig deep into the level of how everything begun, the constituents of this universe which in turn limits what we understand so far. There are still things we don't see remember, dark energy, dark matter, maybe they have effect on gravity. This is what I want to express.
What I wanna say: Don't limit yourself to what the laws says, sometimes they maybe exceptions and that is what science is all about.
Anyways that is why I love science, there is more out there than meets the eye. We have lot more to learn and that is why it is not boring, everyday we progress we learn and we discover new things, we also create history.