The most likely explanation is the prior to perhaps 200 years ago the differentials were different. (Also having lots of children may not result in a lot of descendents, so is an insufficient measure). This would be due to the fact that in an era before universal rights and universal economic security there were reproductive consequences to intelligence (or lack of).

So there is no evolutionary pressure. Evolution is a (brutal) system of unfairness that represents everything that modern progressive values work against. This is something that will need reconciling (or many technologists will hope for genetic engineering I guess) or in the long term will not be sustainable.

Consider your children are on average genetically inferior to you. This is mathematically true. A society which uniformly has 2 children per person + 100% survival will regress. In fact it may take something closer to mediaval or even prehistoric reproductive outcomes to have positive evolutionary pressure. This could be many people having 4-5 children, with many other people who are 'unfit' not having children at all (either remaining childless or dying early).

The subsequent improvements in education,environment and nutrition have likely provided a dividend that masked a fall in underlying genetic intelligence. Naturally as those gains have been fully realised the underlying trend will reassert itself.

People confuse the normative and the descriptive. Everything you say is basicly correct. But it's horrible so it can't possibly be true. But why should evolution not be horrible?

Evolution does not care about our ideology. If we don't account for it and nerf its edge, though forms of selection that don't cause suffering to conscious creatures, like embryo selection or genetic engineering, then we will have to wait for Malthus to provide sufficient selection pressure to ensue our survival or extinction. This fingers-in-ears approach to biological reality would be concerning if countries like Korea and China weren't poised to exploit embryo selection and genetic modification for increased health and IQ, thus likely forcing more reactionary countries like us in the west to adopt them, too.

"if countries like Korea and China weren't poised to exploit embryo selection and genetic modification for increased health and IQ" Increasing IQ could only make sense for me if the society would know how to integrate people with High IQ. But for now we are far from it with 50% of high IQ people failing their education cursus and having issues interacting socially

We will soon have the selection power to select for many traits simultaneously. Also, much of the problem super high IQ people have is the result of being surrounded by people much less capable than themselves. If we seize the high-IQ alleles and distribute them to the proletariat this would not be an issue.

being parent of high-IQ children is quite tiresome compare to average IQ children. So you would need a big bang in term of school reorganization and support to parents.

> there is no evolutionary pressure

Please take another look at my second link: https://en.wikipedia.org/wiki/Cognitive_epidemiology#Overall...

If there's some analysis of evolutionary pressure over time I'd be interested to see it, although I'm not sure it can really be quantified like that.

Whatever the truth, that section is poorly and contradictory.

'A strong link between cognitive ability and the risk of death.'

'A 15-point increase in intelligence was associated with a decreased risk of mortality of 32%.'

Wikipedia suffers a bit from not trying to be too neutral!!

Local cases of intelligence not helping with mortality/reproduction in todays society are not contradictory. This is the (dysgenic) thesis that intelligence does not help. Although increased mortality is perhaps a little harder to explain, but again hardly irreconcilable - I could speculate many plausible explanations.

To address your point, I feel it is intuitively true that we do not have positive evolutionary pressure. If indeed IQs are now falling despite the flynn effect then for intelligence at least here is the evidence for insufficient evolutionary pressure.

I agree that it feels intuitively true, but intuition is often wrong, as that wikipedia section shows. Pay more attention to the sources than the wording of the article. All of the sources demonstrate an inverse correlation between intelligence and mortality, meaning that intelligence does help.

Because birth control is a recent invention. Before that, it took smarts to survive in a crapsack world. We have this stereotype of peasants and medieval people as being stupid in general but all the evidence shows otherwise. You had to be smart and capable of making robust plans to eke out a living on hardscrabble.

Also, until recently mortality rates used to be a lot higher.