Kinship, Models and the Mathematics of Culture
Kin & Number: explainers for students, teachers and curious readers
Contents: every explainer and note on the site
Last update: Oct. 6, 2026
Lecture notes: a self-study route in eight units
Last update: Oct. 14, 2026
Kinship and culture can be reasoned about with care: clear definitions, honest diagrams, worked examples and sources you can check.
Use the menu to find our notation guide, the models you can run in your browser, or to write to us.
New to the field? The book notes group the standard texts by level, from first readings to the algebra of kin terms.
Latest Explainers
A new explainer appears most weeks. Each one ends with its sources, and the arithmetic is small enough to check by hand. Kin-type letters (F, M, B, Z, S, D…) follow our notation guide.
Recent explainers
Last update: Oct. 6, 2026
Small worlds and six degrees: what the folders, the model and the emails showed
Kwame Asante-Boyd
Milgram's folders, the Watts and Strogatz rewiring model worked by hand, the 2003 email study, and what six degrees does and does not mean for villages and kin.
Read the explainer ›Section systems, and how the Kariera and Aranda rules work
Ines Valdera
How four-section (Kariera) and eight-subsection (Aranda) systems work: marriage and descent rules worked by hand, abstract labels, and what the model leaves out.
Read the explainer ›Galton's problem, or why cultures are not independent data points
Leila Farzan
Why cultures are not independent data points: Galton's 1888 objection to Tylor, a worked toy example, and the main fixes from careful sampling to phylogenies.
Read the explainer ›What the evidence says about Dunbar's number
Tomasz Wierzba
Where the 150 in Dunbar's number comes from, the arithmetic behind it, what network studies find, and why a 2021 reanalysis and Dunbar's reply disagree.
Read the explainer ›Cultural consensus analysis, explained with five informants
Leila Farzan
How cultural consensus analysis uses agreement among informants to estimate both what each person knows and the answer key, with a worked five-person example.
Read the explainer ›Agent-based models in anthropology: growing societies from simple rules
Kwame Asante-Boyd
What an agent-based model is, a six-household sharing model to run by hand, the generative idea, Long House Valley and Bali, and how to read a model critically.
Read the explainer ›
Models You Can Run
- Cousin calculator
Second cousin once removed? Count the generations to a shared ancestor and get the name, the relatedness and the expected shared DNA.
- Kinship terms chart
One family tree, six classic systems: see which relatives Eskimo, Hawaiian, Sudanese, Iroquois, Crow and Omaha terms merge or split.
- Network density calculator
Paste who is tied to whom and get density, degree, components and clustering, with every formula shown.
- Pedigree collapse calculator
How many ancestor slots you have at each generation, when they outnumber everyone alive, and how much of your tree is repeats.
- Section system simulator
Moieties, four sections and eight subsections: pick a person and see where their spouse, children and parents fall.
Notes on Classic Problems
Abelian kinship systems, where the order of descent does not matter
When is a man's mother's brother's daughter always in his marriage category? A plain guide to commutative kinship systems, with a six-type worked example.
How age gaps between spouses shape Aboriginal Australian marriage systems
When husbands are much older than wives, which cousin is the right age to marry? Age gaps, polygyny and generations in Aboriginal kinship, worked by hand.
Closed models and open societies in Aboriginal Australian kinship
What closure means for a section system, why real Aboriginal Australian populations were never closed, and how Denham and his critics argued the point.
Measuring shared ideas of identity with consensus analysis
How consensus analysis can study shared ideas about ethnic identity and personhood, with a worked example showing how residual agreement exposes a subculture.
Crow and Omaha kin terms, or why a cousin can be called uncle
In Crow and Omaha terminologies one word can span two generations. A worked example of the skewing, the classic explanations, and newer formal work.
Building a Dravidian kin vocabulary from a few starting terms
Can a whole Dravidian kin vocabulary be built from a few terms and rules? Dwight Read's generative approach, with kin terms derived step by step by hand.
How Dravidian kin terms sort relatives into kin and in-laws
Dravidian kin terms sort every relative into kin or potential in-law. Here is the parity rule behind it, worked by hand, and how scholars put it into algebra.
How to take a kinship terminology apart
What it means to analyze kin terms formally: features, rewrite rules and kin-term algebra, worked on American English, and the long argument over what kinship is.
Herders, farmers and land, and how a conflict model is built
How an agent-based model of mobile herders and settled farmers is set up, what a toy run shows by hand, and what such a model can and cannot say about real conflict.
Kinship networks as channels, and why family loops matter
What it means to treat a kinship network as a set of channels, why P-graphs make marriage loops visible, and a hand count of the loops in a small family.
What mathematics can and cannot settle about kinship
Where formal models help the study of kinship and where they stop: one counting problem, one case no model can settle, and the long argument between the camps.
Nonabelian kinship systems, from the Aranda square to the quaternions
Why the Aranda subsection system does not commute, how the symmetries of a square describe it, and which marriages noncommutative kinship systems allow.
Marriage rules as permutations, and how to count every possible system
How a prescriptive marriage system becomes two permutations and a group, worked through a four-section example, and how to list every possible system.
Kinship, symmetry and what an analogy can prove
Can a kinship system share a structure with DNA or particle physics? Symmetry and groups in plain words, a Dravidian sign rule, and the limits of analogy.
Learning to Labour as a simulation, and what a model of the lads leaves out
How Willis's Learning to Labour might become a simulation: eight pupils and a friendship threshold rule to run by hand, and what such a model tests and flattens.