What are some examples of revered knowledge that turned out to be more fragile than we thought?

I'm working on a Theory of Knowledge essay, and I’m exploring the idea that knowledge we consider revered or unquestionable might actually be more fragile than we assume. I’d love to hear examples from different areas like history, science, or the arts where our understanding or beliefs have shifted over time.

For instance, how has new evidence or changing perspectives revealed the fragility of what was once considered absolute? Looking forward to hearing your insights and any specific examples you can share!