The human lifespan has been extended dramatically over the last 100 years.This is especially true in developed countries.
Average life expectancy at birth in many of these coutries has increased to over 80,and the world average is approaching 70.Before modern times,life expectancy was under 40. However,much of the gain since then has been due to the deline in child deaths.
The life expectancy of adults has not changed as much.For example,a 21 year old male in sixteenth-century England would survive on average for a futher 50 years,giving him a lifespan of 71 years.