Kin selection
The group augmentation hypothesis is not universally accepted by all ethologists, as other well studied explanations for cooperative behaviour exist. Kin selection has been largely proven to be the main driver of the cooperative breeding strategy, through the application of Hamilton's rule across a large variety of studies. Kin selection is the theory that animals act altruistically towards members of their own species in a ratio which is dependent on how genetically related those individuals are to one another. A further criticism of group augmentation predictions replacing or occurring in tandem with kinship, is that the augmentation theory lacks clear empirical data. It is also argued that animals live in groups only for the purpose of an immediate net benefit towards reproductive success. One study of a bird obligate cooperative breeder in particular showed that, while breeding success was dependent on cooperative behaviour, linkage to kinship was ultimately able to explain the behaviour of those species. Overall, literature suggests more empirical data is required for group augmentation theory to be generally accepted.