"[The Dis] wanted their civilization to last forever— that's the one thing we do know about them. They built for the ages in everything they did. The evidence is that they did last a very long time— maybe eighty million years. But early on, they discovered a disquieting truth we are only just learning ourselves. It is this: Sentience and toolmaking abilities are powerful ways for a species to move into a new ecological niche. But in the long run, sentient, toolmaking beings are never the fittest species for a given niche. What I mean is, if you need tools to survive, you're not well fitted to your environment. And if you no longer need to use tools, you'll eventually lose the capacity to create them. It doesn't matter how smart you are, or how well you plan: Over the longest of the long term, millions of years, species that have evolved to be comfortable in a particular environment will always win out. And by definition, a species that's well fitted to a given environment is one that doesn't need tools to survive in it.
"It's the same with consciousness. We know now that it evolves to enable a species to deal with unforeseen situations. By definition, anything we've mastered becomes instinctive. Walking is not something we have to consciously think about, right? Well, what about physics, chemistry, social engineering? If we have to think about them, we haven't mastered them— they are still troublesome to us. A species that succeeds in really mastering something like physics has no more need to be conscious of it. Quantum mechanics becomes an instinct, the way ballistics already is for us. Originally, we must have had to put a lot of thought into throwing things like rocks or spears. We eventually evolved to be able to throw without thinking— and that is a sign of things to come. Some day, we'll become like the people of Dis, able to maintain a technological infrastructure without needing to think about it. Without needing to think, at all…
"The builders of Dis faced a dilemma: The best way to survive in the long run on any world they colonized was to adapt yourself to the environment. The best survivors would be those who no longer needed technology to get by. They tried to outlaw such alterations, but how do you do such a thing for the long term without suppressing the scientific knowledge that makes it possible? Over tens or thousands of millennia, you can only do this by suppressing all technological development, because technologies intertwine. This tactic results in the same spiral into nontechnological life. So inevitably, subspecies appeared that were better survivors in a given locale, because they didn't need technology in that locale. This happened every time, on all their worlds.
"The inhabitants of Dis had studied previous starfaring species. The records are hard to decipher, but I found evidence that all previous galactic civilizations had succumbed to the same internal contradictions. The Dis-builders tried to avoid their fate, but over the ages they were replaced on all their worlds by fitter offspring. These descendents had no need for tools, for culture, for historical records. They and their environment were one. The conscious, spacefaring species could always come back and take over easily from them. But given enough time… and time always passes… the same end result would occur. They would be replaced again. And so they saw that their very strength, the highest attainments they as a species had achieved, contained the seeds of their downfall.
"This discovery finally explained to us why toolmaking species are rare to begin with. It takes an unusual combination of factors to create a species that is fit enough to survive, but at the same time is so unfit in its native environment that it must turn to its weakest organ, its brain, for help. Reliance on tools is a tremendous handicap for any species; only a few manage to turn it into an asset.
"The builders of Dis knew they were doomed. We all are: technological civilization represents a species' desperate attempt to build a bubble to keep hostile environments at bay. Sentient species also never cooperate with one another over the long term, because the environments they need in order to live are incompatible. Some, like the Chicxulub, accept this easily and try to exterminate everyone else. Even they can't stop their own evolution and so eventually they cease to be starfaring species. Destruction or devolution are the only choices."
Karl Schroeder - Permanence