The evolution of matrilineal kinship organization

Abstract

Matrilineal kinship organization is a human social system that emphasizes interactions between matrilineal kin, i.e. individuals related only through females. The 'matrilineal puzzle' refers to the potential for tension characteristic of this social system, owing to the conflict between the interests and responsibilities of men in their roles as brother/uncle versus husband/father. From an evolutionary perspective, matrilineal kinship organization is puzzling when it diverts investment of resources from the individuals who provide the potentially highest reproductive returns. I use a game-theoretic framework to investigate a particular form of matrilineal inheritance-the transfer of property from a maternal uncle to a sororal nephew. The analysis reveals two mechanisms that may make this strategy a stable evolutionary outcome. First, a polygynous male has multiple wives, and hence multiple brothers-in-law; with matrilineal inheritance, each additional brother-in-law may transfer resources to the male's wife's offspring, thus potentially contributing to the male's inclusive fitness. Second, the husband of a polyandrous female is effectively 'sharing' paternity with other men; depending on the number of husbands, he may be better off investing in his sister's offspring. I conclude by discussing how these results address the challenges posed by the occurrence of matrilineal kinship organization.

Genetic relatedness to sisters' children has been underestimated

“…Consequently, their model may overstate the stability of vertical transfers. Similarly, Fortunato [20] shows that selection can favour investment in sisters' children even when . This conclusion is conservative because it also relies on the G78 model.…”

“…It depends instead on the paternity confidence provided by Ego's mother to her husband. The value of h also depends on the number of a woman's husbands [20]. I assume throughout that women have only one.…”

Communal breeding promotes a matrilineal social system where husband and wife live apart

“…However it is not clear why males tolerate a system that favours investment in their sister's rather than their own offspring [8]. Inclusive fitness models do suggest matrilineal inheritance can evolve under very high levels of paternity uncertainty [9,10]; or that matrilineal social organization is only likely to be an evolutionary stable strategy when males are polygynous [11]. Here, we suggest a new hypothesis for a matrilineal bias in male investment, which is that working for sisters can evolve when female kin breed communally.…”

Agency and Adaptation: New Directions in Evolutionary Anthropology

“…Game theory allows one to analyze the consequences of a wide range of strategic interactions and discover whether there are single or multiple equilibria (or none at all, thus providing an analytical basis for indeterminacy). Anthropological applications include collective action problems in resource management, provisioning of public goods, the emergence of institutionalized inequality, and even variation in marriage systems (e.g., Alvard & Nolin 2002, Fortunato 2012, Smith & Choi 2007. Even when interests do not conflict, adaptive consequences of decisions or strategies may depend on what others are doing (known as a coordination game).…”