>>12779450>>12779468Jews underwent extremely rapid positive selection for intelligence, like over 300 years. As a result, they developed a lot of genes which we might consider pathogenic. Take Tay-sachs, lets assume having the disease-causing alleles increase intelligence, and thus heterozygotes have a reproductive advantage. What everyone doesn't talk about is how homozygotes for the diseased alleles have less than 1% HEXA enzyme activity. Now, the HEXA gene is fairly well conserved, even into about 10k years ago, there's actually not a lot of variation in the human HEXA gene.
We see that around 30% of Europeans and 2% of Jews actually do carry a "pseudodeficiency allele" for Tay sachs disease, which decreases enzyme activity, but not enough to cause disease in homozygotes. There are a lot more pseudodeficiency alleles, mainly in the Europeans, which reduce HEXA enzyme activities by varying amounts which we've seen only arise in like the past 500 years, so they're only in like a half of 1% of the European population. In theory, one could actually birth a child with polygenic Tay-sachs disease already, where you have so many pseudodeficiency alleles that it brings enzyme activity to the range of disease, but that's extremely, extremely unlikely with current allele frequencies, which is why it's thought of as almost exclusively a Mendelian disease. Jews actually have fewer pseudodeficiency alleles because pathenogenic heterozygotes can still develop the late-onset form of the disease with the pseudodeficient alleles.
So consider that genetic diseases, even normally ascribed to Jews, are possible to circumvent. In fact, the genes neccessary to replicate the positive effects of Gaucher/Tay-sachs/Niemann-pick disease heterozygotes now exist, but they've taken quite a while to enter the human population, like at least 4k years, and they're like .4% so the pathogenic variants are more of a consequence of unguided extreme selective pressures than the selection itself.
