[ako]

Wikipedia seems to suggest you might be wrong: https://en.wikipedia.org/wiki/Life_expectancy#Variation_over...

For example, for Ancient Rome it says “ while the ~50% reaching age 10 could expect another 40 years of life”.

[jncfhnb]

Hmm I’m surprised.

But if 50% reaches an average age of, say 2, assuming it’s right skewed for those who died before 10; then an average life expectancy of 50 for the remainder means the average life expectancy overall just 26. That squares with the numbers stated I suppose.