You keep calling it a “die off” because you’re being visually tricked by the misleading population pyramid. Use the actuarial tables instead.
Among 65 year old men, the probability of surviving to 75 is 76%. The probability of surviving to 85 is 39%. The probability of surviving to 95 is 5.9%.
For women, the odds are 84%, 52%, and 12% of getting to 75/85/95, respectively.
Yes, these are higher death rates than at younger ages. But nowhere near what the shape of the population pyramid suggests, where the 85 age cohort is about 1/4 as large as the 65, which misleadingly suggests a probability of 25% of living 20 more years, when the real number is closer to 45%.
The Chinese have a method for curing eggs in alkaline solution until they turn black and somewhat translucent, too.
With olives, there’s basically no way to eat them off the tree and have them taste edible. They have to be processed in some way to remove the bitter compounds, usually by brining or curing. So using an alkaline brine is one method, and not that uncommon (even for other colors of olives).
Other uses of alkaline compounds in cooking include using a lye bath for browning for baking pretzels or bagels, certain types of springiness and chewiness for noodles (for example, for fresh ramen), and processing corn into cornmeal through nixtamalization.