Editing Signalling theory (section)

==Costly signalling and Fisherian diploid dynamics==

The effort to discover how costs can constrain an "honest" correlation between observable signals and unobservable qualities within signallers is built on strategic models of signalling games, with many simplifying assumptions. These models are most often applied to [[sexual selection|sexually selected signalling]] in [[diploid]] animals, but they rarely incorporate a fact about diploid sexual reproduction noted by the mathematical biologist [[R.A. Fisher|Ronald Fisher]] in the early 20th century: if there are "preference genes" correlated with choosiness in females as well as "signal genes" correlated with display traits in males, choosier females should tend to mate with showier males. Over generations, showier sons should also carry genes associated with choosier daughters, and choosier daughters should also carry genes associated with showier sons. This can cause the evolutionary dynamic known as [[Fisherian runaway]], in which males become ever showier. [[Russell Lande]] explored this with a [[Quantitative genetics|quantitative genetic]] model,{{sfn|McElreath|Boyd|2007}} showing that Fisherian diploid dynamics are sensitive to signalling and search costs. Other models incorporate both costly signalling and Fisherian runaway.{{sfn|Eshel|Sansone|Jacobs|2002}}{{sfn|Kokko|2002}} These models show that if fitness depends on both survival and reproduction, having [[Sexy son hypothesis|sexy sons]] and choosy daughters (in the stereotypical model) can be adaptive, increasing fitness just as much as having healthy sons and daughters.{{sfn|Eshel|Sansone|Jacobs|2002}}{{sfn|Kokko|2002}}