Why does that matter? There are plenty of natural things that are scary as hell, and plenty of unnatural things that aren't.
The reason you don't see it in nature is that macroscopic organisms never evolved a continuously rotating joint. It's a hard problem for evolution to solve; how would blood vessels cross that boundary?
But of course machines have no such constraints, and the wheel and axle is hardly a new (or scary) invention.
It does not. Once you go through one rotation you've ripped all the muscles and ligaments off, ripped all your skin, and can no longer rotate it any further. Oh, and your entire arm will die in short order because you've ripped all the blood vessels delivering it oxygen.
Is it possible we're talking about two different things? Making a circle with your arm isn't the same as rotating it, and just making a circle isn't particularly useful for flight or locomotion. Imagine attaching a wing to your arm and making a circle -- half the time isn't going to be attacking the wind the wrong way. This wouldn't work to, e.g., fly a helicopter. You need real rotation.
The reason you don't see it in nature is that macroscopic organisms never evolved a continuously rotating joint. It's a hard problem for evolution to solve; how would blood vessels cross that boundary?
But of course machines have no such constraints, and the wheel and axle is hardly a new (or scary) invention.