One of the major claims that Diamond makes in this book is that food production (farming) is one of the major factors that allows a human society to become dominant. Those societies that get food production earliest become the most powerful.
Diamond argues that societies that engage in agriculture become the "haves" of the world. Their agriculture gives them higher population densities. It allows them to become "civilized." When this happens, they develop technology and organized governments. Farming also gives them the infectious diseases that can help to wipe out populations of people who do not farm. In these ways, food production determines the fate of human societies because it is the societies that start to produce food the earliest that come to dominate the world.