Guns, Germs, and Steel Review

I first read Jared Diamond's Guns, Germs, and Steel in the Fall 2003 based on a recommendation from a friend. Many chapters of the book are truly fascinating, but I had criticisms of the book back then and hold even more now. Chief among these is the preponderance of analysis devoted to Papua New Guinea, as opposed to, say, an explanation of the greatly disparate levels of wealth and development among Eurasian nations. I will therefore attempt to confine this review on the "meat and potatoes" of his book: the dramatic Spanish conquest of the Incas; the impact of continental geography on food production; and finally, the origins of the Eurasian development of guns, germs, and steel. In terms of structure, I will first summarize the book's arguments, then critically assess the book's evidentiary base, and conclude with an analysis of how Guns, Germs, and Steel ultimately helps to address the wealth question.
Jared Diamond's fundamental argument in Guns, Germs, and Steel is that Eurasians were able to conquer the Americas, sub-Saharan Africa, and Australia because continental differences set Eurasia on a different, better trajectory than the other continents. His argument addresses a simple question: Why did human development proceed at such different rates on different continents? According to the author, the most important continental differences appear in domesticable plants and animals, germs, orientation of continental axes, and ecological barriers. Throughout the book, he refers back to the "Collision at Cajamarca," or the first encounter between the Incan emperor Atahuallpa and the Spanish conquistador Francisco Pizarro, as a "broad window onto world history." The encounter is effective in capturing his argument, namely that the Spanish "victory" over the Incas was all but a foregone conclusion given the centuries of accumulated benefits conferred on the Europeans by their continental circumstance.
The beneficial continental circumstances enjoyed by