Second step is basically what we have today. Inner monologue etc... He explains as a step above a animal where instead of just instinctively doing something, you have a voice (God, Ancestor, etc) tell you what to do. Fucking great book... If it's right, it helps explain quite a lot mental problems like schizophrenia and Tourettes.
Discussion
Have you seen this piece? https://www.onceinaspecies.com/p/once-in-a-species-73b
TLDR: Our species’ unique success (over other human subspecies) came not from raw IQ, or just tools or language, but from a neural wiring that emphasised abstract thought and a compulsive appreciation of scarce collectibles — enabling the development of proto-money (shell beads), large-scale coordination, and ultimately civilisation.