Life expectancy was low mainly due to childhood diseases
If you lived to 20 you had a pretty good chance of making it to 70
If you lived to 20 you had a pretty good chance of making it to 70
The facts don't quite line up with your belief. In the middle ages, those reaching 20 had an expected remaining life of around 20 years.
“ At age 21, life expectancy of an aristocrat was an additional 43 years.[40]”
Maybe not quite 70, but pretty close