The inclusive fitness of an individual organism is comprised of two components:
1. The successfulness of reproduction and thus the organism genetic contribution and proliferation in the next generation.
2. The number of equivalents of the organism offsrping that share genetic similarities and thus impart the genetic mark of individual into the next generation. Such offspring are gleaned by cooperative behaviors.
Kin selection is a term coined regarding the apparent prioritization of the survival and reproduction of an individual organisms relatives even at the cost of the individuals own survival. The evolution of such a seemingly “altruistic” behavior in different species has puzzled evolutionary biologists and still remains a subject of great debate.
I believe that the model system proposed by Nowak, Tarnita, and Wilson does an adequate job at describing some of the behaviors observed in certain species such as honey bees or certain types of wasps, however there is still probably many components of the behavior mechanisms which we do not yet understand. Thus the model probably will be expanded upon in the near future.
The alternative model proposed in the paper has its merits and potential, and did a good job at ascribing reasons and a evolutionary force behind social species groups. The authors explained that kin selection and inclusive fitness are advantageous to species that survive in close knit environments where cooperation and group living is a staple in life.
For more information please refer to: Nowak, Tarnita, and Wilson, 2010. The Evolution of Eusociality. Nature. 466: 1057-1062.