> Why would all-cause mortality be normally distributed? Erm, that is my point? They're not. The human body has systems that break down. The immune system,

> Why would all-cause mortality be normally distributed? Erm, that is my point? They're not. The human body has systems that break down. The immune system, for example, relies on a fixed number of stem cells that eventually die. Once you have zero of them, you're pretty much done. Also, I seem to remember that our ability to replace fat cells also declines with age (probably for similar reasons). Consequently, outside medical interventions (or lack thereof) aren't really defining human lifetimes.