Nature creates round objects all the time (stones in a river, a hedgehog in a ball,...), but the principle of an axle is not found as far as I know.

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[–] 10 points 2 months ago (2 children)

Wikipedia has a whole article on this subject:

https://en.wikipedia.org/wiki/Rotating_locomotion_in_living_systems

The exceptions it mentions are bacterial flagella and part of the digestive system of some bivalves.

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  • [–] 3 points 2 months ago* (last edited 2 months ago) (1 child)

    yeah thanks for the article! rotating bacterial flagella is what came to my mind as well, but it's microscopically small (i think the flagella is a single macro-molecule?) so i'm not sure whether to include it in the list of (macroscopic) "mechanical rotation"... it's more like biochemical mechanical rotation.

    if we go for biochemical mechanical rotation, there's more: ATP-Synthase is a molecule that sits in cell membranes and that rotates as well each time that a proton passes through it.

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