Jared Diamond’s thesis in Guns, Germs, and Steel is that European economic, military, technological, and political power came about because of geographical luck, and not because the Europeans were in any way culturally or racially superior to people of other parts of the world.
Many people have argued that Europeans came to dominate the world because they were superior to other people. In the past, many people were willing to claim that Europeans were and are racially superior to non-white peoples. More recently, people stopped claiming that but started to argue that European culture was more suited to innovation and technological development than other cultures. Diamond’s thesis is that these arguments are both false and that Europeans got ahead simply because of luck.
In Diamond’s view, power comes from agriculture. Agricultural societies can have large populations that are densely packed. These large populations come about because a relatively few people can farm and, thereby, feed a large number of people who do not farm. Those non-farmers can become artisans who develop technology, scribes who keep written records, bureaucrats who allow centralized governments to function, soldiers who fight wars, and many other things. In this way, agriculture leads to technological, military, economic, and political advantages. (Agriculture also leads to the appearance of infectious diseases like smallpox which helped the Europeans dominate other peoples.)
The question, then, is why Europeans got agriculture before people from areas such as the Americas, Africa, and Australia. Diamond says that this was because of geographic luck. Europeans were lucky enough to live on a landmass where there were many plants and animals that could be domesticated. This was not true of the other continents. This meant that it was easier for Eurasian people to develop agriculture. Europeans were also lucky enough to live on a landmass with a long east-west axis and relatively few physical barriers to movement. This meant that new crops and new technological innovations could easily spread from place to place in Eurasia.
The Europeans came to dominate the world, Diamond says, because they got agriculture before other peoples did. His major thesis is that they got agriculture first because they were geographically lucky, not because they were racially or culturally superior.