Disclaimer: I'm not a researcher in this topic and I have no idea what I'm talking about, just putting my thoughts here

I think that depends on how you define stress? The brain is all electrical signals, so from this simplistic point of view there shouldn't be such thing as "stress", but from my understanding the connections, even though electrical, produce chemical by-products which have to be "flushed away" by the gray matter. This and just human experience suggests brain can get "tired".

However, I don't think the societal problems throughout history had much relevance to the individual stress brains my experience, but more caused by cognitive dissonance when you try to put two conscious beings together, as every brain is different so produces different outputs to same input. Additionally, we still are very much driven by our animal instincts, even though we like to pretend we've "ascended" and have free will.

Now the question is, where can we evolve from here? What evolutionary pressure is there to evolve? We've pretty much peaked as lifeforms, we can dominate any and every environment we want to the point of being detrimental to the Earth itself.

Also this highly scientific documentary I re-watched recently called "Idiocracy (2006)" suggests that higher brain function doesn't necessarily increase the chance of passing genes along, and I tend to agree.