Cooperationisdefinedasanyadaptationthathas
evolved,atleastinpart,toincreasethereproductive
successoftheactor’ssocialpartners.Inclusivefitness
theoryrevealsthatcooperationcanbefavouredbynat-
uralselectionowingtoeitherdirectfitnessbenefits
(mutuallybeneficialcooperation)orindirectfitness
benefits(altruisticcooperation).Directfitnessbenefits
canariseasasimplebyproductofcooperation,orelse
owingtotheexistenceofenforcementmechanisms,
whichmaybefixedorconditionedaccordingtotheindi-
vidual’scooperativebehaviour.Indirectfitnessbenefits
canarisewhencooperationoccursbetweengenetically
similarindividuals,asaconsequenceoflimiteddispersal,
kindiscriminationorgreenbeardmechanisms.These
theoreticalmechanismsareillustratedwithempirical
examples,fromlaboratoryexperimentstofieldstudies.