It’s both 

People in the 1800s lived to 80 or 90 years if they survived as an infant.  

I don't see the connection between the decrease in infant mortality and the increase in average life expectancy. I think it's mainly due to discoveries in the field of medicine, drugs and technology. 

0xbitcoiner

John Adams last day 

July 4, 1826 (aged 90)
Quincy, Massachusetts, U.S.



Most but not all 

John Adams died when he was 90 in 1826


Bell_curve

Yes

Most of that was due to drop in infant mortality. Life expectancy at birth is not meaningful for longevity, especially in prior centuries.


Thanks. Most of that change was due to reduced infant mortality wasn't it?