The five continents to which Jared Diamond refers in Guns, Germs, and Steel are Eurasia, Australia, Africa, North America, and South America. The settlement patterns include humans first appearing in Africa, then expanding to the other continents. Humans went from Africa to Eurasia and Australia, and then to North and South America.
The settlement by humans of the continents resulted in the societies that we now have. Diamond argues in Guns, Germs, and Steel that these geographic trends resulted in variations in terms of which societies proved more technologically advanced than others. For example, he argues that European terrain favored the development of writing and agriculture.
Most books that set out to recount world history concentrate on histories of literate Eurasian and North African societies. Native societies of other parts of the world—sub-Saharan Africa, the Americas, Island Southeast Asia, Australia, New Guinea, the Pacific Islands—receive only brief treatment, namely as concerns what happened to them very late in their history, after they were discovered and subjugated by western Europeans.
The main thrust of Guns, Germs, and Steel is the argument that geography, rather than inherent human traits such as intelligence, determined why European and Asian societies conquered other societies, such as those of Africa. According to this argument, factors outside of humans, such as infectious germs, can take more responsibility for social outcomes than humans themselves.