Punctuated equilibrium (https://en.wikipedia.org/wiki/Punctuated_equilibrium https://en.wikipedia.org/wiki/Punctuated_equilibrium) is an evolutionary hypothesis

Punctuated equilibrium (https://en.wikipedia.org/wiki/Punctuated_equilibrium https://en.wikipedia.org/wiki/Punctuated_equilibrium) is an evolutionary hypothesis that evolution is very slow, except when selection pressures change. If true, the average speed of evolution (in this case, of phenotype) is slow, but highly bimodal (i.e., breakneck or near zero).