One of the many things Jim and I disagree on is the correct stage of ripeness at which to eat a banana. I say it is when it is ripe enough not to take the enamel off your teeth, but before it starts emitting detectable ethanol (or whatever it is that bananas emit that makes then rest of the fruit go rotten) fumes. Jim on the other hand insists that a banana is not edible until its skin is at least 50% black.
This means that any bananas that aren't eaten within a couple of days are left for Jim. This one may have been left just a little too long... Or maybe it's like hanging a brace of pheasant(s?) - when one drops off, you eat the other one.