Abstract and Keywords
This article summarises the common language of multi-level selection theory. Every student of evolution learns that natural selection is based on relative fitness. It doesn't matter how well a trait enhances survival and reproduction, as long as it does so better than alternative traits. Traits that decrease absolute fitness can evolve if they decrease the fitness of everyone else even more. Traits that increase absolute fitness can fail to evolve if they increase the fitness of everyone else even more. Whenever a large population is subdivided into groups, relative fitness in the total population can be divided into two components: relative fitness among individuals within single groups; and relative fitness among groups within the larger population. The fact that the group as a whole suffers from resource overexploitation is irrelevant because natural selection is based only on relative fitness.
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