Estimates of life expectancy (a statistical measure of the average  time an organism is expected to live, based on the year of its birth, its current age, and other demographic factors including gender) in antiquity are far lower than modern values mostly due to the far greater incidence of deaths in infancy or childhood, and those who lived past early childhood had a reasonable chance of living to a relatively old age.
Life expectancy is a statistical measure of the average (see below) time an organism is expected to live, based on the year of its birth, its current age, and other demographic factors including gender. Estimates of life expectancy in antiquity are far lower than modern values mostly due to the far greater incidence of deaths in infancy or childhood. Those who lived past early childhood had a reasonable chance of living to a relatively old age. 
