Science Fair Project Encyclopedia

The Major Transitions in Evolution

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
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.

10-26-2009 08:16:03
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