I found this summary of Eckart’s work. I would like to know a lot more detail about what he wrote. It seems to be almost non-existent in English. As usual, the best German and European thinking is LOST to the English-speaking part of our race. I’m fascinated by this, and anything else we can find on this will be of great interest to me, especially since I have studied Professor Carroll Quigley, who reached the opposite (wrong) conclusion!

Here’s the only piece in English I can find:

Kundenrezension

Volkmar Weiss

5,0 von 5 Sternen Eckart Knaul revitalized
Rezension aus Deutschland vom 23. November 2019Verifizierter Kauf
In 1977 the German physician Eckart Knaul (1921-2002) published his book “Rom: Weltmacht, biologisch gesteuert”. He even paid for an English translation „Rome: a world power biologically influenced” (1987), but did not send copies of this book to libraries in the English speaking world. This is the reason, why Dutton and Woodley of Menie are not aware of Knaul. Otherwise, chapter eleven of their book, entitled “Did other civilisations show a rise and fall in general intelligence”, would have a more substantial background of knowledge.
In 1985 Knaul generalized his insights and published “Das biologische Massenwirkungsgesetz: Ursache von Aufstieg und Untergang der Kulturen“ [The Biological Law of Mass Action: Cause of Rise and Decline of Cultures]. In 1993 followed a second edition, but no English translation.
Knaul understands history as a chain of cyclic events, where in the beginning each cycle is driven by innovation followed by an increase of population. At the peak, we have always overpopulation. In the different social strata high population density and hence high social density leads to different consequences. Those at the top of the social hierarchy, they are the first who feel the growing lack of opportunities and restrict the number of their children, followed by the middle classes. Because general intelligence is correlated with social status, the level of general intelligence of the population is diminishing. Creativity is declining, and the society as a whole steers towards chaos. On this way unrestricted immigration from low-level IQ societies can play an accelerating role.

Searching for the mechanism of rise and fall of empires, in 2004 I became aware of Knauls work. I looked forward to underpin his theory with recent data. As a sidestep, in the novel “Artam” (2007; English translation as an ebook in 2014), written in 2005, I am referring and exploiting Knaul, too. In May 2007 I got for the second time in succession the diagnosis of non-hodgkin lymphoma and did not know, whether I would survive Christmas or not. In the week before I went to the hospital for chemotherapy, I wrote and submitted the paper “The population cycle drives human history – from a eugenic phase into a dysgenic phase and collapse” (2007). The editor of the journal changed the title to “ … eventual collaps”. Dutton and Woodley of Menie refer broadly to this paper, and I having nothing to complain about lacking credit. However this paper is only a kind of summary of a monograph, which I had already in mind in 2007. In 2012 the monograph appeared unter the title “Die Intelligenz und ihre Feinde: Aufstieg und Niedergang der Industriegesellschaft“ [Intelligence and its Enemies: Rise and Decline of Industrial Society]. My original intention to write and to publish this monograph in English I did not realize, because after 2007 I feared a third and deadly wave of lymphoma, limiting my horizon of life.

It is a great pity that either Dutton nor Woodley of Menie are unable to understand German. The knowledge of my monograph with about 2000 references and a lot of data could have led to another quality of their already important work.

Where Knaul sees overpopulation and social density as the forces, regulating from a turning point on a society from rise to fall, the theologian Dutton sees a cycle of religiousness which is only an important concomitant. Underlying the population cycle is always the Aristotelian cycle of political constitutions, form aristocracy and monarchy to democracy and back to dictatorship. The turning point in history is the day where a parliament passes a law to pay benefits for the children of the poor. On this day the breeding for low IQ is beginning, which happened in Prussia in 1891.

Source: https://www.amazon.de/gp/customer-reviews/RO6NPQJZZJGDL?ASIN=184540985X