It may have been stable and dominant in spite of that, like America, currently being run by senile old men. The human mind is a biological computer and it isn’t pretty the older it gets.

https://medium.com/psyc-406-2015/how-fast-does-iq-decline-ca...

Average is probably not what you need to worry about: I'd bet David Attenborough and Mel Brooks still have IQs considerably higher than the average 25-year old. And I'm not convinced IQ is as important as that elusive factor called character.

But you may be right. Maybe what the US really needs is a lagoon.