A historical mystery may be: "why did many hunter-gatherers, or high-activity ancestors of yore, not live healthier lives into their 90s"? The data is scarce, but the picture that is emerging:

A) Some did live into their 90s, but often with "arthritic pain". I remember reading about Daniel Boone (high-activity guy who lived to age 85), who loved to go on hunting trips into his 80s, but was severely limited by arthritis.

B) People of yore may have been limited by unchecked disease and non-optimized diets, but bones of Medieval peasant skeletons also show signs of overuse (lopsided limbs, dislocations, arthritis)

C) Optimizations of exercise may someday include better warnings on overuse of limbs/joints, plus a more optimized diet.