LETTER

Simulation model for kinship structures is ethnographically invalid LETTER Dwight W. Reada,b,1 and Robert Parkinc

The simulation model presented in ref. 1 requires correct are descended, either through father−child filiation usage of kinship concepts. However, the two kinship con- (patrilineal societies) or through mother−child filiation cepts central to the model, the incest taboo and the clan (matrilineal societies) (4). Clans are determined con- form of social organization, are incorrectly presented. ceptually, not through behavior. The authors incorrectly consider the incest taboo The authors incorrectly assume that “siblings of the to express preference for marriages between different opposite sex belong to a different clan by the move of social units: “marriage occurs only with a certain dif- brides to husbands’ lineages” (ref. 1, p. 2380). Instead, ferent cluster, resulting in the incest taboo” (ref. 1, the bride remains a member of her natal clan even after p. 2379). The incest taboo actually refers to the cultural moving in with her husband. Consequently, brother and prohibition of sexual relations between parent and child sister are always members of the same clan, regardless of or between siblings (2) and only affects marriages marriage. Clan marriage exogamy implies a man and his through cultural prohibition of marriages involving in- wife will be in different clans both before and after mar- cestuous sexual relations. riage. A child is always in the clan of its mother or its What the authors call the incest taboo is actually a father. The authors’ model, however, mistakenly implies cultural marriage rule prohibiting within-group mar- “children can belong to different clans from parents by riages, but this does not apply to all lineages. Arabian inheriting traits from both parents” (ref. 1, p. 2381). tribal societies recognize the incest taboo, yet prefer They conclude that a distinction between cross within-lineage marriage between a man and his father’s cousins (parent’s cross-sex sibling’s children) and paral- brother’s daughter, which contradicts the authors’ state- lel cousins (parent’s same-sex sibling’s children) arises ment that “afather’s brother belongs to the same clan [as from the model’s incorrect implication that “women the father], and, thus, marriage with a father’s brother’s change lineages after marriage” (ref. 1, p. 2382). This daughter is prohibited, when the incest taboo is orga- cousin distinction does not derive from the processes nized” (ref. 1, p. 2380). that the authors model but from the generative logic of The authors incorrectly assume behavior patterns a kinship terminology (5–7). lead to cultural prohibitions (1), but the !Kung San, a Their argument (1) that generalized exchange is hunter-gatherer group in Botswana, lack within-group linked with cooperation is confounded by Leach’s marriage, yet have no rule prohibiting such marriages. early work on the Kachin (8); their argument that re- Within-group marriages do not occur due to their cul- stricted exchange is linked with conflict is not ethno- tural rules defining marriageable kin categories (3). graphically realistic; their idea that systems “emerge” The authors mistakenly assume a clan is a cluster in response to cooperation or conflict is exaggerated: of interacting lineages (1). A clan, when it occurs, con- All systems of this sort are subject to both conflict and sists of those lineages that recognize the same apical cooperation. In sum, their models do not correspond ancestor from whom lineage members believe they more than occasionally to actual ethnographic situations.

1 K. Itao, K. Kaneko, Evolution of kinship structures driven by marriage tie and competition. Proc.Natl.Acad.Sci.U.S.A.117,2378–2384. (2020). 2 R. Fox, The Red Lamp of Incest (E.P. Dutton, New York, NY, 1989). 3 D. Read, Kinship based demographic simulation of societal processes. J. Art. Soc. Social Simulation 1, 1 (1998). 4 R. Parkin, Kinship: An Introduction to the Basic Concepts (Blackwell, Oxford, United Kingdom, 1997). 5 D. Read, Kinship theory: A paradigm shift. Ethnology 46, 329–364 (2007). 6 M. Leaf, D. Read, Human Thought and Social Organization: Anthropology on a New Plane (Lexington, Lanham, MD, 2012). 7 D. Read, M. D. Fischer, F. K. L. Chit Hlaing, The cultural grounding of kinship: A paradigm shift. l’Homme 210,63–89 (2014). 8 E. Leach, Political Systems of Highland Burma: A Study of Kachin Social Structure (Harvard University Press, Cambridge, MA, 1954).

aDepartment of Anthropology, University of California, Los Angeles, CA 90095; bDepartment of Statistics, University of California, Los Angeles, CA 90095; and cSchool of Anthropology and Museum Ethnography, University of Oxford, Oxford 0X1 6PE, United Kingdom Author contributions: D.W.R. and R.P. analyzed data and wrote the paper. The authors declare no competing interest. Published under the PNAS license. 1To whom correspondence may be addressed: [email protected].

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