Anthropologist Robin Fox states that "the study of kinship is the study of what man does with these basic facts of life – mating, gestation, parenthood, socialization, siblingship etc." Human society is unique, he argues, in that we are "working with the same raw material as exists in the animal world, but [we] can conceptualize and categorize it to serve social ends." These social ends include the socialization of children and the formation of basic economic, political and religious groups.
anthropology has developed a number of related concepts and terms in the study of kinship, such as descent, descent group, lineage, affinity/affine, consanguinity/cognate and fictive kinship. Further, even within these two broad usages of the term, there are different theoretical approaches.
Kinship can also refer to a principle by which individuals or groups of individuals are organized into social groups, roles, categories and genealogy by means of kinship terminologies. Family relations can be represented concretely (mother, brother, grandfather) or abstractly by degrees of relationship (kinship distance)
In biology, "kinship" typically refers to the degree of genetic relatedness or coefficient of relationship between individual members of a species (e.g. as in kin selection theory). It may also be used in this specific sense when applied to human relationships, in which case its meaning is closer to consanguinity or genealogy.
There is a seventh type of system only identified as distinct later:
Dravidian kinship (the classical type of classificatory kinship, with bifurcate merging but totally distinct from Iroquois). Most Australian Aboriginal kinship is also classificatory.
The six types (Crow, Eskimo, Hawaiian, Iroquois, Omaha, Sudanese) that are not fully classificatory (Dravidian, Australian) are those identified by Murdock (1949) prior to Lounsbury's (1964) rediscovery of the linguistic principles of classificatory kin terms.
Claude Lévi-Strauss argued in The Elementary Structures of Kinship (1949), that the incest taboo necessitated the exchange of women between kinship groups. Levi-Strauss thus shifted the emphasis from descent groups to the stable structures or relations between groups that preferential and prescriptive marriage rules created.
Lévi-Strauss (1949, Les Structures Elementaires), on the other hand, also looked for global patterns to kinship, but viewed the “elementary” forms of kinship as lying in the ways that families were connected by marriage in different fundamental forms resembling those of modes of exchange: symmetric and direct, reciprocal delay, or generalized exchange.
Recognition of fluidity in kinship meanings and relations
Building on Lévi-Strauss's (1949) notions of kinship as caught up with the fluid languages of exchange, Edmund Leach (1961, Pul Eliya) argued that kinship was a flexible idiom that had something of the grammar of a language, both in the uses of terms for kin but also in the fluidities of language, meaning, and networks. His field studies criticized the ideas of structural-functional stability of kinship groups as corporations with charters that lasted long beyond the lifetimes of individuals, which had been the orthodoxy of British Social Anthropology. This sparked debates over whether kinship could be resolved into specific organized sets of rules and components of meaning, or whether kinship meanings were more fluid, symbolic, and independent of grounding in supposedly determinate relations among individuals or groups, such as those of descent or prescriptions for marriage.
The sheer fact of residence in a Bena Bena group can and does determine kinship. People do not necessarily reside where they do because they are kinsmen: rather they become kinsmen because they reside there.” (Langness 1964)
In 1972 David M. Schneider raised  deep problems with the notion that human social bonds and 'kinship' was a natural category built upon genealogical ties and made a fuller argument in his 1984 book A critique of the study of Kinship which had a major influence on the subsequent study of kinship.
Schneider argued that unexamined genealogical notions of kinship had been embedded in anthropology since Morgan's early work because American anthropologists (and anthropologists in western Europe) had made the mistake of assuming these particular cultural values of 'blood is thicker than water', common in their own societies, were 'natural' and universal for all human cultures (i.e. a form of ethnocentrism). He concluded that, due to these unexamined assumptions, the whole enterprise of 'kinship' in anthropology may have been built on faulty foundations. His 1984 book A Critique of The Study of Kinship gave his fullest account of this critique.
Certainly for Morgan (1870:10) the actual bonds of blood relationship had a force and vitality of their own quite apart from any social overlay which they may also have acquired, and it is this biological relationship itself which accounts for what Radcliffe-Brown called "the source of social cohesion". (Schneider 1984, 49)
Schneider himself emphasised a distinction between the notion of a social relationship as intrinsically given and inalienable (from birth), and a social relationship as created, constituted and maintained by a process of interaction, or doing (Schneider 1984, 165). Schneider used the example of the citamangen / fak relationship in Yap society, that his own early research had previously glossed over as a father / son relationship, to illustrate the problem;
The crucial point is this: in the relationship between citamangen and fak the stress in the definition of the relationship is more on doing than on being. That is, it is more what the citamangen does for fak and what fak does for citamangen that makes or constitutes the relationship. This is demonstrated, first, in the ability to terminate absolutely the relationship where there is a failure in the doing, when the fak fails to do what he is supposed to do; and second, in the reversal of terms so that the old, dependent man becomes fak, to the young man, tam. The European and the anthropological notion of consanguinity, of blood relationship and descent, rest on precisely the opposite kind of value. It rests more on the state of being... on the biogenetic relationship which is represented by one or another variant of the symbol of 'blood' (consanguinity), or on 'birth', on qualities rather than on performance. We have tried to impose this definition of a kind of relation on all peoples, insisting that kinship consists in relations of consanguinity and that kinship as consanguinity is a universal condition.(Schneider 1984, 72)
Schneider preferred to focus on these often ignored processes of "performance, forms of doing, various codes for conduct, different roles" (p. 72) as the most important constituents of kinship. His critique quickly prompted a new generation of anthropologists to reconsider how they conceptualized, observed and described social relationships ('kinship') in the cultures they studied.
Janet Carsten employed her studies with the Malays to reassess kinship. She uses the idea of relatedness to move away from a pre-constructed analytic opposition between the biological and the social. Carsten argued that relatedness should be described in terms of indigenous statements and practices, some of which fall outside what anthropologists have conventionally understood as kinship;
Ideas about relatedness in Langkawi show how culturally specific is the separation of the 'social' from the 'biological' and the latter to sexual reproduction. In Langkawi relatedness is derived both from acts of procreation and from living and eating together. It makes little sense in indigenous terms to label some of these activities as social and others as biological. (Carsten 1995, 236)
Philip Thomas' work with the Temanambondro of Madagascar highlights that nurturing processes are considered to be the 'basis' for kinship ties in this culture, notwithstanding genealogical connections
Similar ethnographic accounts have emerged from a variety of cultures since Schneider's intervention. The concept of nurture kinship highlights the extent to which kinship relationships may be brought into being through the performance of various acts of nurture between individuals. Additionally the concept highlights ethnographic findings that, in a wide swath of human societies, people understand, conceptualize and symbolize their relationships predominantly in terms of giving, receiving and sharing nurture.
Notably, Marshall Sahlins strongly critiqued the sociobiological approach through reviews of ethnographies in his 1976 The Use and Abuse of Biology noting that for humans "the categories of 'near' and 'distant' [kin] vary independently of consanguinal distance and that these categories organize actual social practice" (p. 112).
some sociobiologists and evolutionary psychologists to approach human kinship with the assumption that inclusive fitness theory predicts that kinship relations in humans are indeed expected to depend on genetic relatedness, which they readily connected with the genealogy approach of early anthropologists such as Morgan (see above sections). However, this is the position that Schneider, Sahlins and other anthropologists explicitly reject.
In agreement with Schneider, Holland argued that an accurate account of biological theory and evidence supports the view that social bonds (and kinship) are indeed mediated by a shared social environment and processes of frequent interaction, care and nurture, rather than by genealogical relationships per se (even if genealogical relationships frequently correlate with such processes). In his 2012 book Social bonding and nurture kinship Holland argues that sociobiologists and later evolutionary psychologists misrepresent biological theory, mistakenly believing that inclusive fitness theory predicts that genetic relatedness per se is the condition that mediates social bonding and social cooperation in organisms. Holland points out that the biological theory (see inclusive fitness) only specifies that a statistical relationship between social behaviors and genealogical relatedness is a criterion for the evolution of social behaviors.
Holland says, for a full account of kinship in any particular human culture, ethnographic methods, including accounts of the people themselves, the analysis of historical contingencies, symbolic systems, economic and other cultural influences, remain centrally important.
According to an evolutionary psychology hypothesis that assumes that descent systems are optimized to assure high genetic probability of relatedness between lineage members, males should prefer a patrilineal system if paternal certainty is high; males should prefer a matrilineal system if paternal certainty is low. Some research supports this association with one study finding no patrilineal society with low paternity confidence and no matrilineal society with high paternal certainty. Another association is that pastoral societies are relatively more often patrilineal compared to horticultural societies. This may be because wealth in pastoral societies in the form of mobile cattle can easily be used to pay bride price which favor concentrating resources on sons so they can marry.
The evolutionary psychology account of biology continues to be rejected by most cultural anthropologists.
Floyd Lounsbury discovered a seventh, Dravidian referring to Tamil people, type of terminological system that had been conflated with Iroquois in Morgan’s typology of kin-term systems because both systems distinguish relatives by marriage from relatives by descent, although both are classificatory categories rather than based on biological descent.