Editing Unit of selection (section)

== Fundamental theory ==

Two useful introductions to the fundamental theory underlying the unit of selection issue and debate, which also present examples of multi-level selection from the entire range of the biological hierarchy (typically with entities at level ''N''-1 competing for increased representation, i.e., higher frequency, at the immediately higher level ''N'', e.g., organisms in populations or cell lineages in organisms), are [[Richard Lewontin|Richard Lewontin's]] classic piece ''[[The Units of Selection]]''<ref>[[Richard Lewontin|Lewontin, Richard]] 1970. The Units of Selection. [[Annual Review of Ecology, Evolution, and Systematics|''Annual Review of Ecology and Systematics'']] 1: 1-18.</ref> and [[John Maynard-Smith]] and [[Eörs Szathmáry]]'s co-authored book, ''[[The Major Transitions in Evolution]]''. As a theoretical introduction to units of selection, Lewontin writes:
<blockquote>The generality of the principles of natural selection means that any entities in nature that have variation, reproduction, and heritability may evolve. ...the principles can be applied equally to genes, organisms, populations, species, and at opposite ends of the scale, prebiotic molecules and ecosystems." (1970, pp. 1-2)</blockquote>

[[Elisabeth Lloyd]]'s book ''The Structure and Confirmation of Evolutionary Theory'' provides a basic ''philosophical'' introduction to the debate. Three more recent introductions include [[Samir Okasha]]'s book ''Evolution and the Levels of Selection'', Pierrick Bourrat's book ''Facts, Conventions, and the Levels of Selection'', and [[Elisabeth Lloyd]] and Javier Suárez book ''Units of Selection''.