independently from anthropology, biologists studying organisms' social behaviours and relationships have been interested to understand under what conditions significant social behaviors can evolve to become a typical feature of a species (see inclusive fitness theory). because complex social relationships and cohesive social groups are common not only to humans, but also to most primates, biologists maintain that these biological theories of sociality should in principle be generally applicable. the more challenging question arises as to how such ideas can be applied to the human species whilst fully taking account of the extensive ethnographic evidence that has emerged from anthropological research on kinship patterns.