It was discovered some time back that the 'raw score' for IQs was increasing over time - meaning the mean kept going higher and higher. This is called the Flynn Effect. [1] People were getting smarter. The section I linked to is about the fact this trend reversed some time around 1990 in the developed world. Wiki uses weaker language 'possible end' but it's been tested and verified repeatedly at this point - we're getting dumber, and quite rapidly. This remains true even after controlling for obvious explanations like immigration.
This is yet another reason why fertility is, in my opinion, the issue of the century. The world is going to look so absurdly different, and not in a good way, in 50 years, owing to fertility rates alone. We're very likely living on the tail end of a societal golden age.
[1] - https://en.wikipedia.org/wiki/Flynn_effect#Possible_end_of_p...
In the end what is successful is high-functioning sociopaths, that we can find in all high-power places nowadays. Funnily enough, inequality has increased, and now the wealth of your parents determines your life trajectory much more than even 30 years ago. This is really not surprising, once the exploitative sociopath gets in power, they really don't like fair competition that much.
And this is why both IQ and fertility is going down, it is not a future oriented system. It has a lot to do with the capitalist mindset, where we exploit the earth to the point of making it inhabitable at some point...