If you are not familiar with sex, then you need to read more.  In fact, most biological signaling is signalling stake rather than work.  A surfeit of factor A, and insufficiency of factor B, etc.  These conditions may be the result of "work" but there is no contract.

Sex to the side, lots of biological signalling has no probative context.  It's only when there is a competitive antagonism that one is even useful.  The function of PoW/PoS is simply and only to increase the inferred probability that a player is not defecting on a contract of mutual interest, i.e. to establish the reliability of the signal.