The Ratchet of Progress

Weird thoughts occasionally arrive at strange times and without apparent instigation. Such was the case when I was snowbound in a tent recently on Mt. Shasta. I was wondering why societies and civilizations tend to go through periods of enlightenment and progress, then slip into some benighted trend of superstition and irrationality. It made me wonder whether, as a species, humanity (as a whole) has an upper limit on collective reason and rationality.
Intuition suggests that this is not the case because we continue to see scientific progress despite forces (like organized religion) that seek to impede it. Scientific progress is only one aspect of what I'm talking about, though. We have iPods, cell phones, and a space program. We have more sophisticated computers and software. We have advances in medical science. Consider though: have we made much progress in philosophy, public policy, fairness and equality, human rights, eliminating disease and poverty? Have we made much progress in the area of pure reason? In creating a more rational, thoughtful culture? Regretfully, the answer seems to be no.
Robert Pirsig is one of my favorite authors despite having written only two books. In his second book, Lila, Pirsig talks briefly about how a society progresses. Many factors tend to keep a society from moving forward, but it takes someone to posit radical notions well past what society is willing to accept to promote progress. Society considers those notions and moves forward, near them, but ultimately falls back, like a ratchet, to a safer position, (while making some progress). Pirsig didn't talk about an upper limit, though, and I wonder whether he missed something.
Consider history from classical civilizations until today. The Greeks, Romans, Mesopotamians and others had advanced cultures in which reason, science, and the human intellect were valued. At some point, those cultures fell into darkness. Similarly, Europe went through about 500 years of the dark ages (in which religion was the dominant force) and emerged into an age of enlightenment, but I'm not sure it really stuck. In America today we have techno progress in a society in which about 45% of the population doesn't believe in evolution (and are too ignorant and poorly educated to even understand it). We have fallen backwards in terms of the disparity in the distribution of wealth, quality of public education, quality of health care, justice, and divisiveness and intolerance. I believe we are also inching closer to a more draconian, secretive, and facist-like government. Why?
Clearly individuals can make progress and be rational, but maybe societies have a upper limit on collective conciousness and their ability to act rationally. Individuals can discover quantum mechanics and conceive of micro-surgery, but the hive mind can't get beyond some level of superstition and prejudice. I tend to blame religion for a lot of the irrational behavior in the world, but perhaps religion is just a manifestation of humanity's inability to go beyond that upper limit. It's what society uses to ratchet things back.
Twill be sad if true.