[jcranmer]

One possibility is that GP is thinking that "life expectancy was 25, so 20 means you're an old geezer on the deathbed." Alternatively, it may also be a reference to the extreme youth of Alexander the Great, who became king of Macedon at age 20 and proceeded to put down a Greek rebellion and then conquer Thrace, Persia, Egypt, Bactria, cross the Hindu Kush, conquer bits of India (then unknown to the Greeks) and was only stopped from going further when his army said "it's been long enough, can we go home?" He died 3 years later, at age 32. Obviously, he is very much an outlier.

[dredmorbius]

Measures of life expectency are misleading in this regard.

Much of low life expectency comes from very high infant mortality -- deaths to age 5 or 10. Once you've passed that threshold, your odds of survival increase markedly. Perhaps slightly lower than today's first-world standards, but hale-and-hearty at 15 doesn't mean you're going to fall over dead at 25.

You also want to look at life expectency at any given age. And I distantly recall that the number of (I can't remember specifically which) Greeks or Romans surviving to age 80+ compared favourably to modern times.

[YeGoblynQueenne]

Yeah, Alexander was a super hero.

I remember reading stories where he charged ahead of the rest of the army, scaled enemy walls, chased down royal bodyguards and so on. He was bloody crazy. A guy with his (lack of) brains should not have made it past 16, let alone get to 32.

[digi_owl]

A real life example of refuge in audacity?