ABSTRACT
This chapter has both a general and a specific purpose. The general purpose is to show how to reason intuitively about natural selection as a multilevel process. The idea that higher-level units such as social groups can be well adapted, in the same sense that individuals are well adapted, has a long history in biology, the human sciences, and everyday thought. For example, the term “body politic” suggests that a human political organization is comparable to a single organism. In biology, group-level adaptations have been regarded as theoretically possible but sufficiently unlikely that they can be ignored for the majority of species in nature (Williams, 1966). Thus, when most evolutionary biologists reason intuitively about natural selection, they think that it is sufficient to ask, “What traits would maximize the fitness of individuals, relative to other individuals in the population?”
