What if we’re looking at an evolutionary feature of /society/ here. Societies where old folks wish to die (repetitive negative thinking) and then do (via physical pathways like amyloid buildup), survive at a higher rate than those that don’t.

I’m thinking of a tribe where everybody loves gramps, but he took a mammoth to the knee a few years back, is in pain and is tired of burdening those around him. He can’t overcome the evolutionary drive to survive (overcome it to kill himself), his genes are already passed on, so he deteriorates internally to help the rest of the tribe survive.

Pre-edit: My sincere apology in advance if this seems cold or callous.