I’d suggest the book Life Ascending. It talks about how certain major jumps in complexity occurs. It directly addresses the “bumping in the ocean” you mention —

I’d suggest the book Life Ascending. It talks about how certain major jumps in complexity occurs. It directly addresses the “bumping in the ocean” you mention — according to the book the likely explanation was these initial reactions occurred in local environments around certain types of thermal vents that were constrained by small geologic features. Interesting read.