Modern progressivism has led to an increasingly dysgenic reality:
The potential problem was first noted by Galton in 1869. In the 1930s Raymond Cattell was pretty sure that the greater fertility of poorer and duller couples was going to bring down the population average, but was surprised to find that the data showed a contrary trend. Perhaps this was because the effects of copious fertilizer overcame a drop in the quality of the seed, but results are results, and the dysgenic hypothesis looked weak. Of course, to continue the agricultural analogy, yields could also be adversely affected by over-use of pesticides. One possible cause of less capable brains is that these sensitive organs are being poisoned by man-made toxins.
All this and more is covered in the introduction to a new paper:
What Caused over a Century of Decline in General Intelligence? Testing Predictions from the Genetic Selection and Neurotoxin Hypotheses Michael A. Woodley of Menie & Matthew A. Sarraf & Mateo Peñaherrera-Aguirre & Heitor B. F. Fernandes & David Becker
What are we to make of all this? The Woodley et al. argument is that general intelligence, the important and heritable part of mental ability, is falling; and that specific skills, the environmentally-influenced non-heritable part of mental ability, had risen over the last century and is now on a plateau.
The supportive findings are as follows: if you take the g loadings of mental tests (their saturation on the general factor of intelligence) and you link those loadings with the effect sizes of things like inbreeding depression and correlations with motor reaction times, then the strength of selection against intelligence (duller citizens having larger families) is more pronounced on g loaded abilities, but correlates negatively with the Flynn Effect (the secular rise in many, but not all mental tests).
So, it is better to track general ability rather than specific specialised skills.
Well, regardless of whatever might have caused this decline in Western intelligence, it’s nothing that importing a few hundred million sub-85 IQ third-worlders shouldn’t fix, right?