Editing Kin selection (section)

{{Short description|Evolutionary strategy favoring relatives}}
{{good article}}
{{Use British English|date=January 2015}}
[[File:Todd Huffman - Lattice (by).jpg|thumb|upright=1.3|The co-operative behaviour of [[social insects]] like the honey bee can be explained by kin selection.]]
'''Kin selection''' is a process whereby [[natural selection]] favours a trait due to its positive effects on the [[reproductive success]] of an organism's relatives, even when at a cost to the organism's own survival and reproduction.<ref name="West Grifin Gardner 2007">{{Cite journal |last1=West |first1=S. A. |last2=Griffin |first2=A. S. |last3=Gardner |first3=A. |date=March 2007 |title=Social semantics: altruism, cooperation, mutualism, strong reciprocity and group selection |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1420-9101.2006.01258.x |journal=[[Journal of Evolutionary Biology]] |volume=20 |issue=2 |pages=415–432 |doi=10.1111/j.1420-9101.2006.01258.x |pmid=17305808 |s2cid=1792464|url-access=subscription }}</ref> Kin selection can lead to the evolution of [[Altruism in animals|altruistic behaviour]]. It is related to [[inclusive fitness]], which combines the number of offspring produced with the number an individual can ensure the production of by supporting others (weighted by the relatedness between individuals). A broader definition of kin selection includes selection acting on interactions between individuals who share a gene of interest even if the gene is not shared due to common ancestry.<ref name="West Grifin Gardner 2007" />

[[Charles Darwin]] discussed the concept of kin selection in his 1859 book, ''[[On the Origin of Species]]'', where he reflected on the puzzle of sterile social insects, such as [[honey bees]], which leave reproduction to their mothers, arguing that a selection benefit to related organisms (the same "stock") would allow the evolution of a trait that confers the benefit but destroys an individual at the same time. [[J.B.S. Haldane]] in 1955 briefly alluded to the principle in limited circumstances (Haldane famously joked that he would willingly die for two brothers or eight cousins), and [[R.A. Fisher]] mentioned  a similar principle even more briefly in 1930. However, it was not until 1964 that [[W.D. Hamilton]] generalised the concept and developed it mathematically (resulting in '''Hamilton's rule''') that it began to be widely accepted. The mathematical treatment was made more elegant in 1970 due to advances made by [[George R. Price]]. The term "kin selection" was first used by [[John Maynard Smith]] in 1964.

According to Hamilton's rule, kin selection causes genes to increase in frequency when the genetic relatedness of a recipient to an actor multiplied by the benefit to the recipient is greater than the reproductive cost to the actor.<ref name="Hamilton 1964 1–16">{{cite journal |last=Hamilton |first=W. D. |author-link=W. D. Hamilton |year=1964 |title=The Genetical Evolution of Social Behaviour |journal=Journal of Theoretical Biology |volume=7 |issue=1 |pages=1–16 |bibcode=1964JThBi...7....1H |doi=10.1016/0022-5193(64)90038-4 |pmid=5875341 |title-link=The Genetical Evolution of Social Behaviour}}</ref><ref name="Hamilton 1964 17–52">{{cite journal |last=Hamilton |first=W. D. |author-link=W. D. Hamilton |year=1964 |title=The Genetical Evolution of Social Behaviour. II |journal=Journal of Theoretical Biology |volume=7 |issue=1 |pages=17–52 |bibcode=1964JThBi...7...17H |doi=10.1016/0022-5193(64)90039-6 |pmid=5875340}}</ref> Hamilton proposed two mechanisms for kin selection. First, [[kin recognition]] allows individuals to be able to identify their relatives. Second, in viscous populations, populations in which the movement of organisms from their place of birth is relatively slow, local interactions tend to be among relatives by default. The viscous population mechanism makes kin selection and social cooperation possible in the absence of kin recognition. In this case, [[nurture kinship]], the interaction between related individuals, simply as a result of living in each other's proximity, is sufficient for kin selection, given reasonable assumptions about population dispersal rates. Kin selection is not the same thing as [[group selection]], where [[natural selection]] is believed to act on the group as a whole.

In humans, altruism is both more likely and on a larger scale with kin than with unrelated individuals; for example, humans give presents according to how closely related they are to the recipient. In other species, [[vervet monkey]]s use [[allomothering]], where related females such as older sisters or grandmothers often care for young, according to their relatedness. The social shrimp ''[[Synalpheus regalis]]'' protects juveniles within highly related colonies.