The Aztecs were soon dominating Central Mexico, and overawed others as they built and extended their empire. While the capital city housed over 200,000, the valley and its surroundings held an addition million people. Thousands of public buildings, canals, and causeways impressed everyone who came, including the Spanish.
The Maya, Inca, and Aztec empires [were] greatly advanced in the topics agriculture, writing, and engineering and astronomy.
You might think that some kind of dysgenic breeding has kicked in since, but a) there is zero evidence for that, and b) it is more plausible to cite a few negative supply shocks. You know, like the pandemic that wiped out 90 percent of the Aztecs or more, their virtual enslavement by the Spanish, the move from trade-based cities to the isolated hacienda system, and the subsequent malnutrition and demoralization and cultural devastation, all of which amounted to perhaps the most extreme destruction of a civilization ever seen.
James Heckman, Nobel Laureate writes:
This paper develops a model of skill formation that explains a variety of findings established in the child development and child intervention literatures. At its core is a technology that is stage-specific and that features self productivity, dynamic complementarity and skill multipliers. Lessons are drawn for the design of new policies to alleviate the consequences of the accident of birth that is a major source of human inequality.
Try these papers too, plus previous MR posts on the Flynn Effect. IQ is worth talking about, but compare Heckman’s models and data to much of the IQ literature — those models are not very well specified, nor given our current state of knowledge about either growth or IQ can they be — and you’ll see I do mean what I am saying.
If you do wish to try a "genetic argument," there is much more evidence for the "predisposition to debilitating alcoholism" claim. I’d estimate that half of the adult males of Oapan — the village I cite and direct descendants of the Aztec empire I might add — are debilitated alcoholics.
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