Editing Kin selection (section)

===Eusociality===
{{main|Eusociality}}

[[File:Pheidole2.jpg|thumb|[[Ant]]s are [[Eusociality|eusocial]] insects; the queen (large, centre) is reproductive, while the workers (small) and soldiers (medium size, with large [[Mandible (insect mouthpart)|jaws]]) are generally not.]]

[[Eusociality]] (true sociality) occurs in social systems with three characteristics: an overlap in generations between parents and their offspring, cooperative brood care, and specialised castes of non-reproductive individuals.<ref name="Freeman2007">{{cite book |title=Evolutionary Analysis |last1=Freeman |first1=Scott |last2=Herron |first2=Jon C. |year=2007 |edition=4th |publisher=Pearson, Prentice Hall |location=Upper Saddle River, NJ |isbn=978-0-13-227584-2 |page=460 }}</ref> The social insects provide good examples of organisms with what appear to be kin selected traits. The workers of some species are sterile, a trait that would not occur if individual selection was the only process at work. The relatedness coefficient ''r'' is abnormally high between the worker sisters in a colony of [[Hymenoptera]] due to [[Haplodiploid sex-determination system|haplodiploidy]]. Hamilton's rule is presumed to be satisfied because the benefits in [[fitness (biology)|fitness]] for the workers are believed to exceed the costs in terms of lost reproductive opportunity, though this has never been demonstrated empirically. Competing hypotheses have been offered to explain the evolution of social behaviour in such organisms.<ref name=NTW/>

The eusocial shrimp ''[[Synalpheus regalis]]'' protects juveniles in the colony. By defending the young, the large defender shrimp can increase its inclusive fitness. [[Allozyme]] data demonstrated high relatedness within colonies, averaging 0.50. This means that colonies represent close kin groups, supporting the hypothesis of kin selection.<ref name=Colony>{{cite journal |last1=Duffy |first1=J. Emmett |last2=Morrison |first2=Cheryl L. |last3=Macdonald |first3=Kenneth S. |title=Colony defense and behavioral differentiation in the eusocial shrimp ''Synalpheus regalis'' |journal=[[Behavioral Ecology and Sociobiology]] |year=2002 |volume=51 |issue=5 |pages=488–495 |s2cid=25384748 |url=http://www.vims.edu/research/units/labgroups/marine_biodiversity/publications/_pdf/Duffy_et_al_2002_BES.PDF |doi=10.1007/s00265-002-0455-5 |bibcode=2002BEcoS..51..488D |url-status=dead |archive-url=https://web.archive.org/web/20150803214955/http://www.vims.edu/research/units/labgroups/marine_biodiversity/publications/_pdf/Duffy_et_al_2002_BES.PDF |archive-date=2015-08-03 }}</ref>