Simpson, Carl. How many levels are there? How insights from evolutionary transitions in individuality help measure the hierarchical complexity of life . The MIT Press, 2011.
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This chapter argues that the multilevel selection (MLS)-1 to MLS-2 model of a major transition is incomplete because it overlooks a crucial component of fitness. It addresses that the evolution of individuality literature has failed to account for expansive fitness and that expansive fitness differences play an important role in the transition to regimes sensitive to the fitness of the corporate agent. It discusses multilevel evolution during the three phases of transitions in individuality: the aggregate phase, the group phase, and the individual phase. This chapter shows that the path a lineage takes through the phases of transitions is not fixed, but determined by ecology.