In the prologue of Guns, Germs, and Steel, what are the three considerations Diamond talks about as he ponders Yali's question?

In the prologue, Yali asks Diamond three questions:
1) He wanted to know about Diamond's work on guinea birds and how much he was compensated for it.
2)He wanted to know how his people came to populate Papua New Guinea.
3)He wanted to know how white Europeans came to colonize Papua New Guinea within the last 200 years.
From these three questions, Diamond hypothesizes that Yali is really asking a larger question: Why does inequality exist between different cultures? For example, why were Native American, Aboriginal Australian, and African societies colonized by European powers and not the reverse?
In pondering the answer to this question, Diamond discusses the three considerations or objections to studying the question:
1) First, Diamond maintains that, in trying to determine how some societies came to dominate others, some concerned parties conflate an "explanation of causes" with a "justification or acceptance of the results." He argues that this erroneous conclusion about the purposes of historical inquiry is counter-productive. Instead, Diamond insists that anything one learns about the past should be used towards altering disastrous events rather than in perpetuating or repeating genocide, conflict, and hegemony.
2) Second, Diamond insists that his historical treatise is not an "Eurocentric approach to history." Instead, he maintains that his book also discusses relationships between non-European peoples, "especially those that took place within sub-Saharan Africa, Southeast Asia, Indonesia, and New Guinea." By exploring the impact of non-European cultures on European cultures, Diamond asserts that his readers can come to understand how the "basic elements" of Western civilization were imported from other cultures.
3) Third, Diamond argues that his research in no way epitomizes a biased approach towards "civilization." He maintains that he is simply interested in examining the causes for how European powers came to dominate non-European cultures. For his part, Diamond maintains that he doesn't "assume that industrialized states are 'better' than hunter-gatherer tribes, or that the abandonment of the hunter-gatherer lifestyle for iron-based statehood represents 'progress,' or that it has led to an increase in human happiness."
Effectively, in pondering Yali's question, Diamond is most concerned about uncovering pertinent facts rather than relying on preconceived notions about hegemony and civilization. Ultimately, he presents the basic hypothesis for his book:

History followed different courses for different peoples because of differences among peoples' environments, not because of biological differences among peoples themselves.