The Major Transitions in Evolution

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The Major Transitions in Evolution is a book written by John Maynard Smith and Eörs Szathmáry (Oxford University Press, 1995).

Transitions described in the book
Transition from: Transition to: Notes
Replicating molecules "Populations" of molecules in compartments Can't observe
Independent replicators (probably RNA) Chromosomes RNA world hypothesis
RNA as both genes and enzymes DNA as genes; proteins as enzymes
Prokaryotes Eukaryotes Can observe
Asexual clones Sexual populations Evolution of sex
Protists Multicellular organisms — animals, plants, fungi Evolution of multicellularity
Solitary individuals Colonies with non-reproductive castes
Primate societies Human societies with language, enabling memes Sociocultural evolution

Maynard Smith and Szathmary identified several properties common to the transitions:

  1. Smaller entities have often come about together to form larger entities. e.g. Chromosomes, eukaryotes, sex multicellular colonies.
  2. Smaller entities often become differentiated as part of a larger entity. e.g. DNA & protein, organelles, anisogamy, tissues, castes
  3. The smaller entities are often unable to replicate in the absence of the larger entity. e.g. Organelles, tissues, castes
  4. The smaller entities can sometimes disrupt the development of the larger entity e.g. Meiotic drive (selfish non-Mendelian genes), parthenogenesis, cancers, coup d’état
  5. New ways of transmitting information have arisen.e.g. DNA-protein, cell heredity, epigenesis, universal grammar.

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