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).
| 1. | Replicating molecules | to | Populations of molecules in compartments | Can't observe |
| 2. | Independent replicators (probably RNA) | to | Chromosomes | |
| 3. | RNA as both genes and enzymes | to | DNA as genes, proteins as enzymes | |
| 4. | Prokaryotes | to | Eukaryotes | Can observe |
| 5. | Asexual clones | to | sexual populations — evolution of sex | |
| 6. | Protists | to | multicellular organisms — animals, plants fungi evolution of multicellularity | 7. | Solitary individuals | to | colonies with non-reproductive castes | 8. | Primate societies | to | Human societies with language, enabling memes |
Maynard Smith and Szathmary identified several properties common to the transitions:
- Smaller entities have often come about together to form larger entities. e.g. Chromosomes, eukaryotes, sex multicellular colonies.
- Smaller entities often become differentiated as part of a larger entity. e.g. DNA & protein, organelles, anisogamy, tissues, castes
- The smaller entities are often unable to replicate in the absence of the larger entity. e.g. Organelles, tissues, castes
- 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
- New ways of transmitting information have arisen.e.g. DNA-protein, cell heredity, epigenesis, universal grammar.