I assume the person you're responding to is talking more about the aboriginal peoples of the United States.
GG&S is an interesting book, but extremely conjectural and ideological, and not well-sourced. Some of the evidence is distorted. Off the top of my head, he reproduces a table of grain yields, and when tracking down his sources for this, it turns out that he's omitted results that contradict his theory. The reasoning is sometimes shaky or circular: 'Why do we know X wasn't domesticable? Because it wasn't domesticated.' Etc. etc. I don't find his theory holds up particularly well.
GG&S is an interesting book, but extremely conjectural and ideological, and not well-sourced. Some of the evidence is distorted. Off the top of my head, he reproduces a table of grain yields, and when tracking down his sources for this, it turns out that he's omitted results that contradict his theory. The reasoning is sometimes shaky or circular: 'Why do we know X wasn't domesticable? Because it wasn't domesticated.' Etc. etc. I don't find his theory holds up particularly well.