I wouldn't relate the human stupidity to this. I think that even though we're the species that have the greater "inteligence", managing to get the most developed brain in the world, the current cuture praises stupidity. You've probably seen a lot of people saying"f*ck school, f*ck learning, yeah, intelligent people are nerds, f*ck nerds" and etc. So, people want to ignore all the knowledge we've been gathering through all the years our species's been on earth. I call this "the culture of stupidity".
Another thing is, our culture, not only our culture, but our nature seems to make us want to take control of everything in the way we think is better. Basically, even though humans have intelligence and knowledge, they cant only think of what is good for themselves, ignoring every possible negative consequences for others or for the future.
Our nature is also related to war. It seems that most humans alwyas want to fight everything or everyone "in their way", everyone that doesn't agree ofr accpet the way they do things.
The evidences of this, you can see in many societies. We could be saving ourselves and the world if we didn't think about money all the time. Of course, there are many excpetions, but in general, this is the human situation. I don't know how it would've been if the homo neanderthalensis had lived instead of us, homo sapiens sapiens(although tehre is a possibility that we are hybrids of sapiens and neanderthalensis), but one thing I know: The world would be way better if we never existed.
