It wasn't obvious for the first few thousand years. Smart people seemed to make things better. They invented new tools for hunting that could be used as weapons when tribes disagreed. They figured out how to use medicinal plants. They devised languages to convey information from person to person and generation to generation. They invented ways to protect ourselves from the weather, and travel farther with less effort. They gave the gifts of their intellect to people who hadn't thought of those things yet.
No one foresaw that this apparent rising slope of continuous improvement could be the greatest threat to species survival. But so it is.
Smart people invented weapons that enable smaller, weaker people to defeat larger, nastier ones. That works until the larger, nastier ones get the new weapon technology. Or various factions of smaller people decide to throw their weight around, enhanced by technology.
Smart people figured out how to harness various forms of energy. This led to coal mines. Coal mines used to be tunnels that swallowed up hundreds of lives, so smart people figured out how to destroy entire mountains to make a huge, open hole from which to extract coal. Coal is then burned to produce smoke. This smoke contains particles, acids and CO2, all of which destroy the environment surrounding the giant gash that formerly was a forested hill and the fume-belching power plant some distance away.
Smart people invented comfortable clothes that make living in cold climates much more pleasant for those with sensitive skin. They invented motor vehicles, fast ships and aircraft. It's great to be able to get around quickly. We can go visit Aunt Gladys on the other side of the globe and deliver shocking, awesome blasts of hellfire to enemies of our nation from high in the sky or far out at sea. And enemies of our nation can deliver their opinion to us by a number of incendiary methods.
If we could count on smart people to get us out of the jam their smart ideas have created, all would be well. Unfortunately, they have a poor track record in that regard, largely thanks to the larger number of less thoughtful types who are the primary beneficiaries of civilization's amenities. The vast majority of consumers of technology could not and would not have invented it, even if they learn to operate it (and bitch about it) after it has been developed.
It all came to a head on September 11, 2001, when some cave dwellers used a partial skill set to fly some jetliners just well enough to destroy a landmark building and do permanent damage to the national psyche of the United States. We are told by both the cave dwellers and the American intelligence industry that those attacks were just a down payment. The cave dwellers hope to use far more devastating weapons in a future attack.
We are told that the cave dwellers base themselves in the freest lands on Earth: failed states and lawless border lands where the rule of law is enforced by local chieftains and their armed henchmen. Libertarian paradise indeed. The cave dwellers do not establish schools and universities where someone might learn to develop advanced technologies. They use whatever they can piece together, whatever they can keep operating under the challenging conditions of their rustic existence and their fugitive lives when they venture into more scrutinized, civilized nations. Once they have destroyed their enemies, will they be able to maintain a high standard of living? Or will they bid a willing farewell to the technology they no longer need, which they could never have built for themselves in the first place?
If smart people had not invented weapons of mass destruction for their own purposes, these thieves of technology, these suicidal murderers, could not hold those weapons to our heads. They would be forced to fight more openly.
Meanwhile, civilization fouls itself with the waste products of its own rich diet. Anyone willing to take less sees it grabbed and gobbled by someone all too willing to take more. All this was invented by well-meaning smart people.
If small, smart people had not invented ways to hold off big, dumb people, big dumb people would have made small, smart people extinct long ago. No one would miss them if they had never been allowed to flourish. Anti-intellectualism, relentlessly pursued, would have brought stability that attempts at universal education never will.
Getting back on that track will be unpleasant and possibly completely catastrophic. It certainly won't be any fun for those trying to enjoy a few pleasant years before extinction, especially when the reaper shows up for them. Because so much firepower has been built in the last century, the superstitious idiots who want to use it have plenty of it to use, as soon as they manage to get their hands on it. And even of they don't, the needs of the "the economy" demand that we continue to despoil the planet anyway.
All this brought to you by human intelligence. We know so much, but so many don't seem to know any better.