Original: Proceedings of the National Academy of Sciences 104 : 9736-9740 In this case , an individual 's inclusive fitness varies depending on how much it invests in within-group competition ( e.g. hoarding a private food cache ) versus between-group competition ( e.g. contributing to common foraging ) ; and on its relatedness to the other group members .
Simplified: In their model , an individual 's inclusive fitness varies depending on how much it invests in within-group competition ( e.g. hoarding a private food cache ) versus between-group competition ( e.g. contributing to common foraging ) ; and on its relatedness to the other group members .