[beefman]

Are you thinking of Kuhn's paradigm shifts?[1]

Or the closely-related concept of punctuated equilibria?[2][3]

[1] https://en.wikipedia.org/wiki/Paradigm_shift

[2] https://en.wikipedia.org/wiki/Punctuated_equilibrium

[3] https://www.youtube.com/watch?v=mcAq9bmCeR0