Change is a given. Everything changes and we need to accept that. Groups of people share ideas about the world and our understanding of it. This shared understanding can be cultural, political, scientific, religious and numerous other forms of understanding the world, it's workings and human interaction. Each individual in a group might have a slightly different understanding of a given thing, but the aggregate of these understandings come together to form a shared outlook. Often this can be in the form of a narrative; a shared story that explains a certain phenomena that each individual accepts.
Evolution is the small incremental changes to how we see things. This is not the evolution of Darwin. In the Darwinian sense, the organisms with adaptations best suited to their environments flourish, over very long periods of time small successful adaptions compound into new species. The evolution of our understanding is the small changes driven by different voices as some take greater influence and others lose their influence. It can take the form of refinement, problems are encountered and solved. The narrative slowly shifts as the solutions to problems are incorporated into the group understanding.
Sometimes problems pile up and it's not possible to solve them with the current way of thinking. Things get stuck and the current narrative can't be expanded to incorporate all the differences. This might cause a split, with different groups going in different directions, taking the narrative in different incompatible ways. But sometimes the current way of thinking becomes entrenched and the only way to progress is revolution. This is a complete shift in the group understanding to something incompatible with the previous view. The narrative completely changes. This shift is often violent and unpredictable.
A community can fall into disarray and will require a revolution to fix it???