old people as shock observers

In 2011, Charles Goodnight and I had an idea about how post-reproductive life span might evolve, an idea that sounds pretty unlikely in the abstract, but when we did the numbers, it actually panned out. An older, “retired” segment of the population, we argued, serves to keep the population stable over cycles of feast and famine. When times are good, they eat the excess food and help prevent population overshoot. When food is scarce, they are the first to die.

Josh Mitteldorf & Dorion Sagan - Why Aging Isn't Inevitable

What a fascinating insight! Old people exist not for some higher cultural need, but for the simple need of population regulation.

Considering the fact that even some types of worms have post-reproductive life spans, our capacity for generational knowledge transfer is probably an exaptation rather than an adaptation.