title: Major evolutionary transitions in individuality.
abstract: The evolution of life on earth has been driven by a small number of major evolutionary transitions. These transitions have been characterized by individuals that could previously replicate independently, cooperating to form a new, more complex life form. For example, archaea and eubacteria formed eukaryotic cells, and cells formed multicellular organisms. However, not all cooperative groups are en route to major transitions. How can we explain why major evolutionary transitions have or haven't taken place on different branches of the tree of life? We break down major transitions into two steps: the formation of a cooperative group and the transformation of that group into an integrated entity. We show how these steps require cooperation, division of labor, communication, mutual dependence, and negligible within-group conflict. We find that certain ecological conditions and the ways in which groups form have played recurrent roles in driving multiple transitions. In contrast, we find that other factors have played relatively minor roles at many key points, such as within-group kin discrimination and mechanisms to actively repress competition. More generally, by identifying the small number of factors that have driven major transitions, we provide a simpler and more unified description of how life on earth has evolved.
authors.affiliation: Department of Zoology, University of Oxford, Oxford OX1 3PS, United Kingdom; Magdalen College, Oxford OX1 4AU, United Kingdom; stuart.west@zoo.ox.ac.uk.
authors.forename: Stuart A
authors.initials: SA
authors.lastname: West
authors.affiliation: Department of Zoology, University of Oxford, Oxford OX1 3PS, United Kingdom;
authors.forename: Roberta M
authors.initials: RM
authors.lastname: Fisher
authors.affiliation: School of Biology, University of St. Andrews, Dyers Brae, St. Andrews KY16 9TH, United Kingdom; and.
authors.forename: Andy
authors.initials: A
authors.lastname: Gardner
authors.affiliation: Institute of Ecological Sciences, Faculty of Earth and Life Sciences, Vrije Universiteit, 1081 HV, Amsterdam, The Netherlands.
authors.forename: E Toby
authors.initials: ET
authors.lastname: Kiers
mesh_terms: D000818:Animals; D005075:Biological Evolution; D003142:Communication; D003299:Cooperative Behavior; D004171:Diploidy; D004463:Ecology; D005260:Female; D040961:Genetic Drift; D006238:Haploidy; D006801:Humans; D007206:Individuality; D008297:Male; D012919:Social Behavior; D013559:Symbiosis / Q000502:physiology*
keywords: altruism; conflict; cooperation; division of labor; signaling