this is all veyr vague so I dont what exactly youre referring to.... but I find its main points impressive in their inherently reliable certitude....
for example
without large, domesticatable animals to plow, you would have to do it with human labour - huge difference
and 'crop'-compatible, nutritious plants - without those, you have to gather (or small-scale agriculture), and get far less nutrition per human labour
If you happen to have large domesticatable beasts of burden, and plants you can use in large-scale agriculture that are highly nutritious and 'efficient' in terms of labour... Those are obviously ENORMOUS advantages, and granted by the environment, geography
I know of and have heard of no other way to produce so much food with such a small portion of society's resources, and no way of avoiding or dismissing the central importance of that factor in the development Diamond talks about (who conqeurs who)
Thats just the abstract theory....... real world history also happens to conform very nicely with the hypothesis