It also mentioned that life expectancy in 1900 in the USA was 47 and now it is 79. But much of that is because infant mortality has fallen. With fewer babies dying before age 1 or 5, that will cause the average to go up.
But what if we look at people who make it past their infancy? See Life Expectancy by Max Roser of Our World in Data. Excerpt:
"Child mortality is defined as the number of children dying before their 5th birthday. To see how life expectancy has improved without taking child mortality into account we therefore have to look at the prospects of a child who just survived their 5th birthday: in 1841 a 5-year old could expect to live 55 years. Today a 5-year old can expect to live 82 years. An increase of 27 years.Those numbers are for England and Wales.
At higher ages mortality patterns have also changed. A 50-year old could once expect to live an additional twenty years. Today the life expectancy of a 50-year old has increased to an additional 33 years."
There is much more interesting information at that site along with some great charts and graphs.
Here are links to two other views:
Human Lifespans Nearly Constant for 2,000 Years by Benjamin Radford, Live Science Contributor.
Human lifespans have not been constant for the last 2000 years by John Hawks. He is Professor of Anthropology at the University of Wisconsin.
(Hat tip: Ashley Powell, one of my students, who sent me all these links)