This is the study btw :
Social Epistasis Amplifies the Fitness Costs of Deleterious Mutations, Engendering Rapid Fitness Decline Among Modernized Populations (2017)
https://link.springer.com/article/10.1007/s40806-017-0084-x

The basic theory of the "social epistasis amplification model (SEAM)" is that harmful genetic mutations in group-living animals (e.g. humans) don't just harm the individual carrying said mutations, but damage the overall reproductive fitness of their entire group (e.g. a human society or country), including those who don't carry said mutations.

Biologically maladaptive people ("spiteful mutants") disrupt societal processes and institutions that enforce or encourage evolutionarily adaptive behavior (e.g. religious institutions, marriage, etc.) for a variety of reasons. Maybe they are mentally ill, ugly, have an inferiority complex, feel socially maligned in some way, and so on — all signs of poor genetic health caused by a high level of harmful mutations.

Feminist cat ladies are a good example of this phenomenon: They prey on young women who would usually get married and have children (evolutionarily adaptive behavior) and convince them to become whores who abort all of their babies (extremely maladaptive behavior).

The study posits that SEAM may explain the Behavioral Sink phenomenon that was exposed by Calhoun's "Rat Utopia" experiments. Calhoun put rats in an enclosure and gave them unlimited resources, causing their population to boom. At a certain population size, the rats became completely dysfunctional: They exhibited sexual perversions, suffered spontaneous miscarriages, did not raise their litters, killed their own offspring, some became cannibals, some became frenetically overactive, others completely retreated from society, and so on.

Previously, Behavioral Sink was attributed to the negative psychological impact of overpopulation, but this study argues that the rats experienced a "mutational meltdown." Basically, Calhoun removed natural selection from the equation, enabling rats with harmful or maladaptive genetic mutations to survive into adulthood and reproduce. Each subsequent generation became progressively more genetically damaged until the Spiteful Mutant rats reached a critical mass, whereby their maladaptive behavior influenced the entire colony, at which point, the Rat Utopia collapsed and the entire population went extinct.

Westerners currently live in the human equivalent of Calhoun's Rat Utopia and we're seeing very similar results today.