Is this really all that surprising? We have a ton of things ongoing now that we either know or suspect are big contributors to this: - the whole male loneliness epidemic - a longstanding loss of community and social organizations around the country - a pretty terrible job market for many Americans - plenty of things to be stressed or worried about. Geopolitical instability. Erosion of individual rights. The complete…
On the other hand historically there's been circumstances far worse than we are having now in terms of war, famine, diseases, living standards and it didn't stop people from reproducing at all. I really doubt it's that. I think it's something else.
Just because those are the most interesting events to study doesn't mean that in the past countries were constantly experiencing war, famine and epidemics. There were plenty of calm, relatively peaceful periods in between.
As far as living standard are concerned, while being a peasant was hard work during certain periods such as harvest and sowing, outside of those periods farmers actually worked less hours than we do today. That leaves lots of time to help out with chores in your village and maintain relationships with the people around you.