Just a little point that the life expectancy given there is "at birth" and unless I'm mistaken, it's the mean. Which means infant mortality contributes enormously to this figure. It's a misconception that in the past you would only rarely see someone much older than 50. I'm not sure how this would affect the analysis. But it's worth bearing in mind. I'm sure there were plenty of great grandparents before 1900. That usage of great seems to stem from the 1500s. https://www.etymonline.com/word/great-grandfather#etymonline...