Jared Diamond’s thesis in Guns, Germs, and Steel is that the countries of the world that became rich and powerful did so because of geographical luck. These countries did not become rich and powerful due to racial or cultural reasons. They did not become rich and powerful because they were better than other countries. Instead, they were simply lucky in terms of where they happened to be located relative to things like important natural resources.
When Diamond was working as a biologist in New Guinea, a New Guinean man named Yali asked him why whites were so rich and New Guineans were so poor. Diamond started to think about this question and eventually wrote this book to present his answer. Diamond wants to refute the idea (held by many people) that European countries became rich and powerful because they were somehow superior to other cultures. Many people have thought that Europeans were racially superior to other groups and/or that Europeans had a better culture. Diamond strongly disagrees with this suggestion.
Diamond’s thesis is that geographic luck was what made some countries rich and powerful and others weak and poor. He says that the countries that became rich and powerful were those that developed agriculture first. When countries developed agriculture, they were able to make large, complex societies. In those large, complex societies, they were able to develop technologies that made them powerful. Their wealth and power stemmed from their early adoption of agriculture.
But why did these countries get agriculture first? Diamond’s thesis is that they were simply lucky. These countries happened to be located in places where there were a large number of plant and animal species that could be domesticated. They were located in places where it was easy for these domesticated species to spread from one society to another. Because of this luck, they developed agriculture and, thereby, became rich and powerful.
Diamond’s thesis, then, is that geographic luck played the largest role in determining which countries would become rich and powerful and which would remain relatively poor and powerless.