Editing Evolutionary game theory (section)

==Signalling, sexual selection and the handicap principle==
[[File:Peacock at Warwick Castle.jpg|thumb|The peacock's tail may be an instance of the [[handicap principle]] in action]]
{{main|Signalling theory}}

Aside from the difficulty of explaining how altruism exists in many evolved organisms, Darwin was also bothered by a second conundrum – why  a significant number of species have phenotypical attributes that are patently disadvantageous to them with respect to their survival – and should by the process of natural section be selected against – e.g. the massive inconvenient feather structure found in a peacock's tail.  Regarding this issue Darwin wrote to a colleague "The sight of a feather in a peacock's tail, whenever I gaze at it, makes me sick."<ref>Pallen, Mark, ''The Rough Guide to Evolution'', Penguin, 2009, p.74, {{ISBN|978-1-85828-946-5}}</ref>  It is the mathematics of evolutionary game theory, which has not only explained the existence of altruism, but also explains the totally counterintuitive existence of the peacock's tail and other such biological encumbrances.

On analysis, problems of biological life are not at all unlike the problems that define economics – eating (akin to resource acquisition and management), survival (competitive strategy) and reproduction (investment, risk and return). Game theory was originally conceived as a mathematical analysis of economic processes and indeed this is why it has proven so useful in explaining so many biological behaviours.  One important further refinement of the evolutionary game theory model that has economic overtones rests on the analysis of costs.  A simple model of cost assumes that all competitors suffer the same penalty imposed by the game costs, but this is not the case. More successful players will be endowed with or will have accumulated a higher "wealth reserve" or "affordability" than less-successful players.  This wealth effect in evolutionary game theory is represented mathematically by "[[resource holding potential]] (RHP)" and shows that the effective cost to a competitor with a higher RHP are not as great as for a competitor with a lower RHP.   As a higher RHP individual is a more desirable mate in producing potentially successful offspring, it is only logical that with sexual selection RHP should have evolved to be signalled in some way by the competing rivals, and for this to work this signalling must be done ''honestly''. [[Amotz Zahavi]] has developed this thinking in what is known as the "[[handicap principle]]",<ref>{{cite journal | last1=Zahavi | first1=A. | year=1975 | title=Mate selection – a selection for a handicap | journal=Journal of Theoretical Biology | volume=53 | issue=1| pages=205–214 | doi=10.1016/0022-5193(75)90111-3 | pmid=1195756| bibcode=1975JThBi..53..205Z | citeseerx=10.1.1.586.3819 }}</ref> where superior competitors signal their superiority by a costly display.  As higher RHP individuals can properly afford such a costly display this signalling is inherently honest, and can be taken as such by the signal receiver.  In nature this is illustrated than in the costly plumage of the [[peacock]].  The mathematical proof of the handicap principle was developed by [[Alan Grafen]] using evolutionary game-theoretic modelling.<ref name="Grafen 1990 517–546">{{cite journal |author-link=Alan Grafen |last=Grafen |first=A. |year=1990 |title=Biological signals as handicaps |journal=Journal of Theoretical Biology |volume=144 |issue=4 |pages=517–546 |doi=10.1016/S0022-5193(05)80088-8 |pmid=2402153|bibcode=1990JThBi.144..517G }}</ref>