Diamond will use two major types of research tools in his attempt to answer Yali's question.
First, he will use tools from the "hard sciences." He will study things like the size of seeds of various grasses in different areas of the world. He will look at the evolutionary strategies of microbes. These are research tools taken from the biological sciences.
Second, he will use tools from the social sciences. Here, he will use thought experiments and natural experiments. He will, for example, look at the spread of Polynesians across the Pacific. He will look at how their societies differed from one another based on the environments in which they ended up. He will also try to do things like categorizing civilizations, as when he differentiates between bands, tribes, chiefdoms, and states in Chapter 14.