There are many historical figures mentioned in Diamond’s study. Some—such as the philosophers Aristotle, Plato, and Rousseau—are included because of their theories of how societies are formed, which Diamond then refutes. Other people, such as Atahuallpa, the last Incan king, are used as examples of how one society conquered another. Atahuallpa was held captive by Spanish conquistador Francisco Pizarro, who demanded “history’s largest ransom” in gold. After Pizarro received everything he asked for, he killed Atahuallpa anyway. Even though Pizarro had the weaponry to destroy the Incas, through this act, Diamond recounts, Pizarro demoralized the Incas, causing their complete collapse.

Another factor in Pizarro’s victory over the Incas was the use of horses. Even though the Incas outnumbered the Spaniards five hundred to one, the combination of the Spaniards’ guns and soldiers on horses proved lethal. This same advantage was used, Diamond points out, against the Native American people in North America and is the reason behind their all but total collapse. One exception, Diamond writes, was the Sioux (Lakota) victory over General George Custer’s US Army battalion at the famous battle of Little Big Horn in 1876. The reason, however, for the Native American victory was their adoption of technology. “Thanks to their mastery of horses and rifles, the Plains Indians of North America, the Araucanian Indians of southern Chile, and the Pampas Indians of Argentina fought off invading whites longer than did any other Native Americans,” Diamond writes.

Other explorers—Christopher Columbus, James Cook (in the Hawaiian Islands), Hernan Cortés (in Central America), and Hernando de Soto (in North America)—are briefly mentioned, as are the catastrophic effects they had on the societies they encountered. Also included in Diamond’s discussions are important inventors, such as Thomas Edison (phonograph), Johannes Gutenberg (printing press), and the Wright brothers (airplane) as the author explains the advancement of technology.

The lives and influences of leaders such as King Kamehameha I, first ruler of the Hawaiian Islands, are explored, as are the cultural effects of Karl Marx, Joseph Stalin, Adolf Hitler, King Sejong of Korea, George Washington, and John F. Kennedy, to name a few.

But it is not just individuals who are discussed. Diamond explores groups of people as well. This includes the already mentioned Maori of New Zealand, the Incas of South America, and the Aztecs of Central America. The development of Aboriginal societies in Australia is explored not only from ancient times but also up to the current underclass status Aborigines suffer in modern times. Likewise, the various tribes of people in Africa provide source material for the study of languages, diet, and agriculture. Indigenous people of the North American continent are studied, with special attention given to the original and ancient Clovis people, as well as the more modern Black Foot tribe, the Cherokee and Navajo, and the Inuit.

Diamond pays special attention, toward the end of his book, to the people of the African continent. Most Europeans and Americans, Diamond contends, know Africans only in connection with the slave trade and their resultant, uprooted cultures. However, Diamond points out that the African continent has an extremely diverse geography as well as the world’s longest prehistory, which has resulted in a very diverse population. At one point, Diamond focuses on the Khoisan of southern Africa, a group made up of two types of people: large-bodied herders called Khoi and small-sized hunter-gatherers called San. The skin of Khoisan people is not black but rather yellowish. Similar to the story of conquest between the Maori and the Moriori people in New Zealand, the Bantu people of the central area of the African continent, Black farmers who were more developed agriculturally, eventually overcame the Khoisan, who relied more on hunting and gathering practices.

In the end, whether Diamond focuses on individuals or discusses groups of people, his conclusions affect all of humankind. So, in a sense, the people featured in Guns, Germs, and Steel include everyone who has ever lived.