Related, my favorite paper title of all time, "Robust Soldier Crab Ball Gate" [1], demonstrating how soldier crabs can perform functionally complete reversible computations.
Another way to put it: each step in a reversible process must be a bijection, or "information-preserving". The naive way to do that is to return the entire input as part of the result, but that's missing the point.
[1] https://arxiv.org/abs/1204.1749