Over the arc of time, I’m not sure that an accurate characterization is that humans have been getting dumber and dumber. If that were true, we must have been super geniuses 3000 years ago!
I think what is true is that the human condition and age old questions are still with us and we’re still on the path to trying to figure out ourselves and the cosmos.
I definitely think we are smarter if you are using IQ, but are we less reactive and less tribal? I'm not so sure.
That's my theory, anyway.
In my opinion, this is a uniquely human thing because we're smart enough to develop technologies with planet-level impact, but we aren't smart enough to use them well. Other animals are less intelligent, but for this very reason, they lack the ability to do self-harm on the same scale as we can.