One of my covid projects was to look into economic theories of "long cycles", which... go back a long time. I haven't got up to Turchin, but here's some notes for anyone who's interested... (sorry not well cited, but I think direct searches will yield supports for all claims).

There's an idea of "saecula" for the ancients: that humans go through cycles because we collectively forget lessons learned, most commonly after the last who witnessed the actual events dies, ~100yrs. The word meaning changed to mean knowledge caught up in an age, that which does not transcend like God's. Hence the modern usage of secular.

For the moderns, there's an economic idea like this that I think matriculates in German Empire/1850s-WWI...

(aside: I'm astonished the more I learn about what was a super-fecund school of thought centered 1850ish at Germany/U. Humboldt, Berlin and near schools, with many well-known names in politics and the humanities: Bismark, Hegel, Marx, Bauer, Stirner, Nietzsche. And the beginning of modern physics: Plank, Einstein, Helmholtz, Boltzman, Ernst, the list basically just goes on and on; and also the beginning of the modern practice of standard doctoral/masterly degrees in the academy.)

The reason for the context is that I think it's this combo of humanities and sciences that leads to an important development: "Kathedersozialisten" (armchair social philosophers) who were very concerned with the engineering/mechanism of _society_. i.e. They are the beginning of who we know as modern economists: heavy on math and data and they begin to notice patterns...

(aside: Marx is half in this tradition: Kapital reflects Smith's eye to data, but then he bails on this in preference for his linear history as, I think, it enables his revolutionary goals.)

What they got out of an early statistical analysis of historical wealth (equity, prices, interest rates) and social dynamics (like invention, booms, busts, unrest/warfare) is that there are regular cycles. Measurable in the data. This begins to be described by Schumpeter, esp the short ~10yr "business cycle" of boom/recession, tho he also comments on the longer cycles and their international character. I think maybe this is part of Austrian economics, and that there are some political-economic reasons on the way to the world wars to explain why the American/British/French traditions don't accept this knowledge until recently.

It's picked up by Kondatriev in 1950s Stalinist Russia, who pays more attention to the long cycles as a lens into Capital analysis and development of the capitalist state. As noted, Stalin (after Marx) wanted a linear end-of-history development/confrontation with "the old modes" of capitalist thought; but Kondatriev managed to keep an open mind, learned from the data, and came up with his "K-waves" theory of 50/100/150 year long economic cycles. (He paid for his open mind with his life.)

Since, Josh Goldstein's thesis (MIT/Stanford '89) is a great recap and update for the American empire and more rigorous statistical analysis of ~500 years of price/interest/invention/war data.

Today, Ray Dalio is the CO of Bridgewater, the world's largest hedge fund: he has a blog series on long-cycles on LinkedIn (tho unfortunately doesn't cite any of this there) and basically says we're in the falling part of a 150 year hegemonic cycle and that it's gonna get grim. And all these other guys would agree! Goldstein has been commenting on the 2020s since the 1980s.

Could it really be that our current pandemic and economic recession/depression were somehow caused together? Should we expect major wars soon? How unlikely is it that this all happened 100 years ago, and 100 years before that? (the exceptionally large cholera epidemic in 1830s Europe in the aftermath of Napoleonic wars)

In this light, it seems a reasonable hypothesis that these four: economic hardship/famine, disease, war and death; do indeed travel together, caused by people forgetting to take them seriously and therefore suffering a terrible judgement. Ofc, that's just the ancient idea of apocalypse at the end of an age.