"Cargo" refers to all the material goods a society develops and produces. Early on in Guns, Germs, and Steel, Jared Diamond is questioned by a New Guinean named Yali. He asks why Western society has developed so much more cargo than that of New Guinea. Diamond details this cargo as

material goods whose value New Guineans instantly recognized, ranging from steel axes, matches, and medicines to clothing, soft drinks, and umbrellas. In New Guinea all these goods were referred to collectively as "cargo."

Diamond comes to understand that cargo is only the most visible tip of the iceberg of European societies' abilities to establish dominance in the world.

Diamond states that for a long time, genetic superiority was posited as an answer for Europe's success, but he says that this theory has been soundly disproven. He also points to a cold-climate theory, one that argues that Europeans advanced so rapidly because frigid weather forced them to innovate and develop technology to survive the rigors of the region. Long periods of cold, this theory asserts, also gave people the time to think and develop new ideas.

Diamond says, however, that this theory has also been largely discredited. For example, he notes that until about 1,000 years ago, northern Europeans contributed nothing "of value" to world civilization despite the cold weather. He also notes that other groups living in very cold climates have not necessarily become technologically advanced.

Searching for other, more plausible answers led Diamond to the writing of this book.