Research in anthropology has shown that kin terminologies have a complex combinatorial structure and vary systematically across cultures. This article argues that universals and variation in kin terminology result from the interaction of (1) an innate conceptual structure of kinship, homologous with conceptual structure in other domains, and (2) principles of optimal, “grammatical” communication active in language in general. Kin terms from two languages, English and Seneca, show how terminologies that look very different on the surface may result from variation in the rankings of a universal set of constraints. Constraints on kin terms form a system: some are concerned with absolute features of kin (sex), others with the position (distance and direction) of kin in “kinship space,” others with groups and group boundaries (matrilines, patrilines, generations, etc.). Also, kin terms sometimes extend indefinitely via recursion, and recursion in kin terminology has parallels with recursion in other areas of language. Thus the study of kinship sheds light on two areas of cognition, and their phylogeny. The conceptual structure of kinship seems to borrow its organization from the conceptual structure of space, while being specialized for representing genealogy. And the grammar of kinship looks like the product of an evolved grammar faculty, opportunistically active across traditional domains of semantics, syntax, and phonology. Grammar is best understood as an offshoot of a uniquely human capacity for playing coordination games.

Jones introduces an intricate machinery of kin classification that overcomes limitations of previous accounts. I question whether such a machinery is plausible. Because individuals never need to learn the entire spectrum of kin terminology, they could rely on data-driven learning. The complexity of Jones's machinery for kin classification casts doubt on the existence of innate structures that cover the complete linguistic domain.

In this commentary, I focus on Jones' suggestion of a close connection between the domain of space and that of kinship. I expand on that suggestion by introducing the concept of frame of reference and show how it can possibly participate to the generation of kinship systems.

To establish Optimality Theory as a framework in anthropology, or as a general model of higher human cognition, researchers have to demonstrate OT is convincing in a number of ways. This commentary summarizes some of them – based on experience obtained in contemporary linguistic OT – including factorial typologies, exact formulation of candidate sets and constraints, and computational plausibility.

The target paper claims to contribute to the conceptualisation of kinship but is, in fact, only concerned with descriptive kinship terminologies. It uses Optimal Theory to analyse this vocabulary but it is not clear if this is to be understood as a psychological phenomenon. Jones does not make clear how this special vocabulary might relate to kinship in general.

Integral to the discipline of anthropology are both science and holism. The application of Optimality Theory to two partial kin terminologies narrows analysis to descriptive value, fragments phenomena, and constrains data selection, which precludes significant knowledge. Embedded in this critique is a call to move analysis from fragment to whole and from descriptive features to deeper levels of knowledge underlying kin terms, thereby leading to a cognitive path for holistic understanding of human phenomena.

We suggest that there are two coordination games when it comes to understanding kin terminology. Jones' article focuses on the linguistic coordination inherent in developing meaningful kin terminologies, alluding briefly to the benefits of these kin terminologies for coordination in other domains. We enhance Jones' discussion by tracing the links between the structure of kin terminologies and their functions.

The target article offers an analysis of the categorization of kin types and empirical evidence that cross-cultural universals may be amenable to OT explanation. Since the analysis concerns the structuring of conceptual categories rather than the use of words, it differs from previous OT analyses in lexical semantics in what is considered to be the input and output of optimization.

Kinship systems are best explained functionally, in terms of the conflicting needs of the society concerned, rather than in terms of universal constraints, whether Optimality Theory or other; but OT is particularly unsuitable as it rules out taxonomies. A conceptual analysis of kinship terminology shows, not that “grammar” extends to kinship, but that general cognition has the formal power to handle grammar.

Explanations in the domain of kinship can be sought on several different levels: Jones addresses online processing, as well as issues of origins and innateness. We argue that his framework can more usefully be applied at the levels of developmental and historical change, the latter especially. A phylogenetic approach to the diversity of kinship terminologies is most urgently required.

Jones's analysis of Seneca kinship semantics gets some of the facts about close relatives wrong, and his mechanism for extending the analysis to distant relatives does not work.

Common to language and kinship is digital format. This is a discovery, not an innate feature of human cognition. But to produce a testable model, we need Darwinian behavioural ecology.

I raise issues concerning Jones' Seneca analysis, its relationship to analyses of Dravidian-, Crow-, and Omaha-type systems. These affect the convincingness of his kinship study, and thus the wider conclusions that he wants to draw regarding human cognition and language.

Jones' article suggests that the anthropological analysis of kinship has followed a single line of development based on a single underlying conception of meaning and method. In fact, there have been two opposed lines of development. Jones' conception is positivistic. The other is pragmatic. Pragmatic theory is superior on every recognized criterion. This briefly describes the differences.

Jones's system of constraints promises interesting insights into the typology of kin term systems. Three problems arise: (1) the conflation of categories with algorithms that assign them threatens to weaken the typological predictions; (2) OT-type constraints have little psychological plausibility; (3) the conflation of kin-term systems and kinship systems may underplay the “utility function” character of real kinship in action.

We designed an experiment to test the application of optimality theory (OT) in kinship terminology studies. Specifically, we examined the OT constraints within a set of behavioral data using Chinese kin terms. The results from this behavioral approach support and extend Jones' linguistic approach by identifying underlying cognitive mechanisms that can explain and predict behavioral responses in kinship identification.

The choice of emphasis in kinship studies has often resulted in incompatible theoretical models of kinship that are mutually undermining and contradictory. Jones' attempts to reconcile disparate approaches to kinship using OT is useful, however; seeing kinship as a specialized system for representing genealogy may be unwarranted in the light of recent advances in mathematical approaches to kinship terminologies.

While the idea of applying Optimality Theory to kinship has potential, this commentary draws attention to problems with the constraints proposed. Particularly, Distinguish Matrikin appears to recapitulate an error of linking matrilineal descent to Iroquois kinship too closely and more generally mixing descent with true kinship parameters.

Jones argues that extending Seneca kin terms to second cousins requires a revised version of Optimality Theoretic grammar. I extend Seneca terms using three constraints on expression of markers in nested binary classification trees. Multiple constraint rankings on a nested set coupled with local parity checking determines how a given kin classification grammar marks structural endogamy.

Jones uses a mechanism from the linguistic theory, Optimality Theory, to generate the range of kin systems observed in human cultures and human languages. The observed distribution of kinship systems across human societies suggests that some possibilities are preferred over others, a result that would indicate Jones' model needs to be refined, especially in its treatment of markedness.