Editing Unit of selection (section)

{{short description|Biological entity within the hierarchy of biological organization}}
{{more citations needed|date=March 2018}}
[[File:Wilson's Matryoshka Doll Multilevel Selection Model.jpg|thumb|upright=1.3|[[David Sloan Wilson]] and [[Elliott Sober]]'s 1994 Multilevel [[natural selection|Selection]] Model, illustrated by a nested set of Russian [[matryoshka doll]]s. Wilson himself compared his model to such a set.]]
A '''unit of selection''' is a [[biological]] entity within the hierarchy of [[biological organization]] (for example, an entity such as: a [[RNA world hypothesis|self-replicating molecule]], a [[gene]], a [[cell (biology)|cell]], an [[organism]], a [[Group selection|group]], or a  [[species]]) that is subject to [[natural selection]]. There is debate among evolutionary biologists about the extent to which evolution has been shaped by selective pressures acting at these different levels.<ref name="okasha2006">Okasha, S. (2006) ''Evolution and the levels of selection''. Oxford University Press.</ref><ref name=HullLangmanGlenn2001>{{cite book |title=Science and Selection: Essays on biological evolution and the philosophy of science |chapter=Chapter 3: A general account of selection |author1=Hull, David L. |author2=Langman, Rodney E. |author3=Glenn, Sigrid S. |publisher=Cambridge University Press |year=2001 |isbn=9780521644051 |chapter-url-access=registration |chapter-url=https://archive.org/details/scienceselection0000hull }}</ref><ref>{{Cite journal|last1=Zee|first1=Peter|last2=Dyken|first2=J. David Van|last3=Bever|first3=James D.|last4=Richerson|first4=Peter J.|last5=Fletcher|first5=Jeffrey A.|last6=Linksvayer|first6=Timothy A.|last7=Breden|first7=Felix|last8=Fields|first8=Peter|last9=Edmund D. Brodie Iii|date=February 2010|title=Multilevel and kin selection in a connected world|journal=Nature|language=en|volume=463|issue=7283|pages=E8–E9|doi=10.1038/nature08809|pmid=20164866|pmc=3151728|issn=1476-4687|bibcode=2010Natur.463....8W}}</ref>

There is debate over the relative importance of the units themselves. For instance, is it group or individual selection that has driven the evolution of [[altruism]]? Where altruism reduces the fitness of ''individuals'', individual-centered explanations for the evolution of altruism become complex and rely on the use of [[game theory]],<ref name=MaynardSmith>{{cite book |title=Minds, Machines and Evolution |editor=Hookway, Christopher |author=Maynard Smith, John |author-link=John Maynard Smith |chapter=The evolution of animal intelligence |chapter-url=https://books.google.com/books?id=bb86AAAAIAAJ&q=%22I+turn+now+to+evolutionary+game+theory%22&pg=PA64 |page=64 |isbn=9780521338288 |year=1986|publisher=CUP Archive }}</ref><ref name= Dugatkin>{{cite book |title=Game Theory and Animal Behavior |editor1=Dugatkin, Lee Alan |editor2=Reeve, Hudson Kern|chapter-url=https://books.google.com/books?id=ldmRTvHAFFQC&pg=PA52 |page=52 |author=Dugatkin, Lee Alan |chapter= §3.2.3 Category III: Group selection |isbn=9780195350203 |year=1998 |publisher=Oxford University Press |quote=group-selected cooperation can always be cast within some broad-based individual selection model}}</ref> for instance; see [[kin selection]] and [[group selection]]. There also is debate over the definition of the units themselves,<ref>{{Cite book|last=Bourrat|first=Pierrick|date=August 2021|title=Facts, Conventions, and the Levels of Selection|url=https://www.cambridge.org/core/elements/facts-conventions-and-the-levels-of-selection/8EAF88974A3BE92761217A2EC6AB4634|access-date=2021-08-23|website=Elements in the Philosophy of Biology|doi=10.1017/9781108885812 |isbn=9781108885812 |s2cid=238732212 |language=en}}</ref> and the roles for selection and replication,<ref name=HullLangmanGlenn2001/> and whether these roles may change in the course of evolution.<ref name=Sydow>{{cite book |title=From Darwinian Metaphysics towards Understanding the Evolution of Evolutionary Mechanisms. A Historical and Philosophical Analysis of Gene-Darwinism and Universal Darwinism |author=von Sydow, Momme |publisher=Universitaetsverlag Goettingen Press |year=2012 |page=481 |isbn=978-3863950064}}</ref>