The other explanation I’ve heard bandied about is a polygenic version of sickle-cell anemia (where being heterozygous for the allele protects you from malaria but being homozygous gives you an awful disease).
In this model, there are a bunch of alleles that all push the phenotype in roughly the same direction, and having some of them is good, but past some threshold fitness starts rapidly declining.
(Further speculation: the optimum threshold is higher in the environment of civilization than in the ancestral environment, so these genes are experiencing massive positive selection over the last 10,000 years.)
This isn’t a causal explanation, but it differs from the tower-foundation model in claiming that there’s not a separate weakness to go looking for, just an optimum that’s being surpassed- especially when two people near the optimum have children.
The other explanation I’ve heard bandied about is a polygenic version of sickle-cell anemia (where being heterozygous for the allele protects you from malaria but being homozygous gives you an awful disease).
In this model, there are a bunch of alleles that all push the phenotype in roughly the same direction, and having some of them is good, but past some threshold fitness starts rapidly declining.
(Further speculation: the optimum threshold is higher in the environment of civilization than in the ancestral environment, so these genes are experiencing massive positive selection over the last 10,000 years.)
This isn’t a causal explanation, but it differs from the tower-foundation model in claiming that there’s not a separate weakness to go looking for, just an optimum that’s being surpassed- especially when two people near the optimum have children.