Yali is described by Diamond in the Prologue to Guns, Germs, and Steel as a "remarkable local politician" in New Guinea, where the author was doing field research on bird evolution. Diamond writes that Yali, a very intelligent and perceptive man, was asking him "lots of probing questions." Perhaps the deepest of these questions was the one that forms the inquiry at the heart of Guns, Germs, and Steel:
Why is it that you white people developed so much cargo and brought it to New Guinea, but we black people had little cargo of our own?
By "cargo," Diamond writes, Yali meant material goods, the trappings of technology, "ranging from steel axes, matches, and medicines to clothing, soft drinks, and umbrellas." As Diamond perceived it, this very simple question "went to the heart of life as Yali experienced it," and it raised very significant questions about the course of human history in general. Diamond says that Guns, Germs, and Steel was written as an attempt to provide an answer to Yali's question, which really interrogated the sources of human inequality on a global scale. The book's argument—in short, that human inequality was essentially the result of geographic accident—is Diamond's answer, one which is intended to undercut spurious claims of European racial and cultural superiority.