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Chapter Summary

  1. Major transitions in evolution include: (a) the origin of self-replicating molecules capable of heredity, (b) the transition from RNA as the catalyst and genetic material, to protein as the catalyst and DNA as genetic material, (c) the origin of the first cells, (d) the emergence of eukaryotic cells, (e) the evolution of sexual reproduction, (f) the evolution of multicellular organisms, (g) the evolution of developmental complexity within multicellular organisms, (h) the evolution of individuality, (i) the evolution of groups, including complex societies, and (j) the evolution of eusocial societies, with a division of labor and sterile workers.
  2. Many of the major transitions in evolution share a common structure and lead to common consequences. Each transition possesses some of the following processes (most feature all of them): (a) individual agents give up the ability to reproduce independently, and they join together to form a larger aggregate ensemble with a shared reproductive fate; (b) once individual agents form these higher-level aggregations, they are able to take advantage of economies of scale and efficiencies of specialization; and (c) the processes of aggregation and specialization facilitate changes in information technologies.
  3. Eukaryotes may have emerged from a fusion between an ancient bacterium and an ancient archaeal cell. This fusion likely involved some sort of endosymbiosis.
  4. Endosymbiosis may also have been involved in the evolution of organelles, including mitochondria and chloroplasts, as well as some components of the cell nucleus.
  5. Early on, during the evolution of multicellularity, cells may very well have joined together and disbanded often, forcing us to view early multicellularity as a temporary, rather than a fixed, condition.
  6. The evolution of individuality involved the transfer of fitness from the individual cell to the multicellular organism. This transfer of fitness involved the differentiation of cell lines into those specialized in reproduction (germ cells) and those specialized in maintenance and growth of the organism (somatic cells).
  7. Living in groups requires a degree of sociality that is not required for solitary living, and this also often entails new levels of coordination and communication between individuals to obtain such benefits. Group living typically imposes costs in addition to providing benefits.