And how did it happen?
Ddarwin himself had big doubts about that, as well as Stephen Gould. Gould came up with his “punctuated equilibrium “ to try to explain Cambrian - but it proved insufficient.
I used to believe in Darwin’s theory, after reading “Darwin’s Doubt “, I’ve become a strong skeptic.
Makes sense if the theory is true.
There must have been countless dead-end half-creatures that simply couldn't survive.