For millennia, if not for eons—anthropology continuously pushes backward the time of human origin—life expectancy was short. The few people who grew old were assumed, because of their years, to have won the favor of the gods.
The typical person was fortunate to reach 40.
Beginning in the 19th century, that slowly changed. Since 1840, life expectancy at birth has risen about three months with each passing year. In 1840, life expectancy at birth in Sweden, a much-studied nation owing to its record-keeping, was 45 years for women; today it’s 83 years.
The United States displays roughly the same trend. When the 20th century began, life expectancy at birth in America was 47 years; now newborns are expected to live 79 years. If about three months continue to be added with each passing year, by the middle of this century, American life expectancy at birth will be 88 years. By the end of the century, it will be 100 years.
Viewed globally, the lengthening of life spans seems independent of any single, specific event. It didn’t accelerate much as antibiotics and vaccines became common. Nor did it retreat much during wars or disease outbreaks. A graph of global life expectancy over time looks like an escalator rising smoothly. The trend holds, in most years, in individual nations rich and poor; the whole world is riding the escalator.
Read the full, original story: What happens when we all live to 100?