Formation of human kinship structures depending on population size and cultural mutation rate.

How does social complexity depend on population size and cultural transmission? Kinship structures in traditional societies provide a fundamental illustration, where cultural rules between clans determine people's marriage possibilities. Here, we propose a simple model of kinship interactions that considers kin and in-law cooperation and sexual rivalry. In this model, multiple societies compete. Societies consist of multiple families with different cultural traits and mating preferences. These values determine interactions and hence the growth rate of families and are transmitted to offspring with mutations. Through a multilevel evolutionary simulation, family traits and preferences are grouped into multiple clans with interclan mating preferences. It illustrates the emergence of kinship structures as the spontaneous formation of interdependent cultural associations. Emergent kinship structures are characterized by the cycle length of marriage exchange and the number of cycles in society. We numerically and analytically clarify their parameter dependence. The relative importance of cooperation versus rivalry determines whether attraction or repulsion exists between families. Different structures evolve as locally stable attractors. The probabilities of formation and collapse of complex structures depend on the number of families and the mutation rate, showing characteristic scaling relationships. It is now possible to explore macroscopic kinship structures based on microscopic interactions, together with their environmental dependence and the historical causality of their evolution. We propose the basic causal mechanism of the formation of typical human social structures by referring to ethnographic observations and concepts from statistical physics and multilevel evolution. Such interdisciplinary collaboration will unveil universal features in human societies.

The slave trade and the origins of matrilineal kinship.

Matrilineal kinship systems-where descent is traced through mothers only-are present all over the world but are most concentrated in sub-Saharan Africa. We explore the relationship between exposure to Africa's external slave trades, during which millions of people were shipped from the continent during a 400-year period, and the evolution of matrilineal kinship. Scholars have hypothesized that matrilineal kinship, which is well-suited to incorporating new members, maintaining lineage continuity and insulating children from the removal of parents (particularly fathers), was an adaptive response to the slave trades. Motivated by this, we test for a connection between the slave trades and matrilineal kinship by combining historical data on an ethnic group's exposure to the slave trades and the presence of matrilineal kinship following the end of the trades. We find that the slave trades are positively associated with the subsequent presence of matrilineal kinship. The result is robust to a variety of measures of exposure to the slave trades, the inclusion of additional covariates, sensitivity analyses that remove outliers, and an instrumental variables estimator that uses a group's historical distance from the coast as an instrument. We also find evidence of a complementarity between polygyny and matrilineal kinship, which were both social responses to the disruption of the trades. This article is part of the theme issue 'Social norm change: drivers and consequences'.

Emergence of kinship structures and descent systems: multi-level evolutionary simulation and empirical data analysis.

In many indigenous societies, people are categorized into several cultural groups, or clans, within which they believe they share ancestors. Clan attributions provide certain rules for marriage and descent. Such rules between clans constitute kinship structures. Anthropologists have revealed several kinship structures. Here, we propose an agent-based model of indigenous societies to reveal the evolution of kinship structures. In the model, several societies compete. Societies themselves comprise multiple families with parameters for cultural traits and mate preferences. These values determine with whom each family cooperates and competes, and they are transmitted to a new generation with mutation. The growth rate of each family is determined by the number of cooperators and competitors. Through this multi-level evolution, family traits and preferences diverge to form clusters that can be regarded as clans. Subsequently, kinship structures emerge, including dual organization and generalized or restricted exchange, as well as patrilineal, matrilineal and double descent systems. These structures emerge depending on the necessity of cooperation and the strength of mating competition. Their dependence is also estimated analytically. Finally, statistical analysis using the Standard Cross-Cultural Sample, a global ethnographic database, empirically verified the theoretical results. Such collaboration between theoretical and empirical approaches will unveil universal features in anthropology.

Evolution of kinship structures driven by marriage tie and competition.

The family unit and kinship structures form the basis of social relationships in indigenous societies. Families constitute a cultural group, a so-called clan, within which marriage is prohibited by the incest taboo. The clan attribution governs the mating preference and descent relationships by certain rules. Such rules form various kinship structures, including generalized exchange, an indirect exchange of brides among more than two clans, and restricted exchange, a direct exchange of brides with the flow of children to different clans. These structures are distributed in different areas and show different cultural consequences. However, it is still unknown how they emerge or what conditions determine different structures. Here, we build a model of communities consisting of lineages and family groups and introduce social cooperation among kin and mates and conflict over mating. Each lineage has parameters characterizing the trait and mate preference, which determines the possibility of marriage and the degree of cooperation and conflict among lineages. Lineages can cooperate with those having similar traits to their own or mates', whereas lineages with similar preferences compete for brides. In addition, we introduce community-level selection by eliminating communities with smaller fitness and follow the so-called hierarchical Moran process. We numerically demonstrate that lineages are clustered in the space of traits and preferences, resulting in the emergence of clans with the incest taboo. Generalized exchange emerges when cooperation is strongly needed, whereas restricted exchange emerges when the mating conflict is strict. This may explain the geographical distribution of kinship structures in indigenous societies.

Feeding practices, healthcare and kinship during the first year of life / Alimentação, cuidado em saúde e parentesco durante o primeiro ano de vida

This paper reports a study of how babies are fed during their first year of life as practiced by families living in a low-income neighborhood of Salvador, Bahia, Brazil and served by the state's Family Health Program. Two families were followed up over a year using the Bick method for the observation of mother-infant relationships. The results showed that although the families appreciated the recommendations of health professionals regarding the need to practice exclusive breastfeeding until the child reached six months, in practice during their first few weeks of life the babies were started on complementary food in addition to breast milk. The mothers made decisions regarding feeding the babies taking into consideration the following: The opinions of a selection of relatives; food availability; ideas about what is suitable for the developing baby; and finally, their observations of the child's responses. The results show that food is part of the mutually imbricated processes of the social construction of the person and the constitution of kinship ties. The conclusion reflects on the implications of these findings for health practices...

Realizou-se um estudo sobre a alimentação durante o primeiro ano de vida em famílias que moram em um bairro de baixa renda em Salvador atendido pelo Programa de Saúde da Família. Participaram duas famílias que foram acompanhadas ao longo de um ano. Os dados foram coletados utilizando o método Bick de observação da relação mãe-bebê. A análise dos relatos das visitas teve como referência a técnica de análise de conteúdo. Os resultados evidenciam que, embora as famílias valorizem as prescrições de profissionais de saúde sobre a prática do aleitamento materno exclusivo até os seis meses, desde as primeiras semanas os bebês recebem alimentos em forma complementar ao leite materno. As decisões sobre a alimentação são tomadas pelas mães, considerando: opiniões de vários parentes, disponibilidade de alimentos, idéias sobre o que é adequado para o desenvolvimento do bebê, assim como a observação das respostas da criança. Mostra-se que a alimentação faz parte do processo de construção social da pessoa e dos laços de parentesco. Finalmente são tecidas reflexões sobre as implicações destes resultados para as práticas de saúde...

Feeding practices, healthcare and kinship during the first year of life / Alimentação, cuidado em saúde e parentesco durante o primeiro ano de vida

This paper reports a study of how babies are fed during their first year of life as practiced by families living in a low-income neighborhood of Salvador, Bahia, Brazil and served by the state's Family Health Program. Two families were followed up over a year using the Bick method for the observation of mother-infant relationships. The results showed that although the families appreciated the recommendations of health professionals regarding the need to practice exclusive breastfeeding until the child reached six months, in practice during their first few weeks of life the babies were started on complementary food in addition to breast milk. The mothers made decisions regarding feeding the babies taking into consideration the following: The opinions of a selection of relatives; food availability; ideas about what is suitable for the developing baby; and finally, their observations of the child's responses. The results show that food is part of the mutually imbricated processes of the social construction of the person and the constitution of kinship ties. The conclusion reflects on the implications of these findings for health practices.(AU)

Realizou-se um estudo sobre a alimentação durante o primeiro ano de vida em famílias que moram em um bairro de baixa renda em Salvador atendido pelo Programa de Saúde da Família. Participaram duas famílias que foram acompanhadas ao longo de um ano. Os dados foram coletados utilizando o método Bick de observação da relação mãe-bebê. A análise dos relatos das visitas teve como referência a técnica de análise de conteúdo. Os resultados evidenciam que, embora as famílias valorizem as prescrições de profissionais de saúde sobre a prática do aleitamento materno exclusivo até os seis meses, desde as primeiras semanas os bebês recebem alimentos em forma complementar ao leite materno. As decisões sobre a alimentação são tomadas pelas mães, considerando: opiniões de vários parentes, disponibilidade de alimentos, idéias sobre o que é adequado para o desenvolvimento do bebê, assim como a observação das respostas da criança. Mostra-se que a alimentação faz parte do processo de construção social da pessoa e dos laços de parentesco. Finalmente são tecidas reflexões sobre as implicações destes resultados para as práticas de saúde.(AU)

O fenômeno da acomodação familiar em pais/mães de pacientes com transtorno obsessivo-compulsivo / Parenthood and family accommodation in relatives of patients with obsessive-compulsive disorder

Um dos fenômenos mais frequentes nas famílias de pacientes com Transtorno Obsessivo-Compulsivo é a acomodação familiar: participação nos rituais do paciente e modificações na rotina, contribuindo para o desencadeamento e a manutenção dos sintomas. Nesta pesquisa, verificou-se o grau de acomodação familiar apresentado por doze mães e dois pais, selecionados por meio da aplicação da Medida de Criticismo Percebido aos pacientes. Os familiares responderam à Escala de Acomodação Familiar. Os resultados foram analisados em torno de quatro temáticas: 1) participação nos rituais obsessivo-compulsivos do(a) paciente; 2) modificações na rotina familiar; 3) desgaste na família; 4) grau de perturbação do(a) paciente quando não atendido(a) em suas solicitações. De 70 respostas, 78,6 por cento afirmaram a participação nos rituais obsessivo-compulsivos; de 56 respostas, 78,6 por cento disseram haver modificações na rotina familiar; 100,0 por cento das respostas indicaram desgaste na família e 83,3 por cento mostraram que o paciente perturba os familiares quando não é atendido em suas solicitações.

One of the most frequent phenomena in the families of obsessive-compulsive disorder patients is Family Accommodation: participation in the patient's rituals, with modifications to the routine, which contributes to reinforcing and maintaining the symptoms. This study aimed to evaluate the level of Family Accommodation presented by 12 mothers and 2 fathers, selected from the Measure of Perceived Criticism applied to the patients. Results were analyzed according to four dimensions: 1) participation in patient's obsessive-compulsive rituals; 2) modifications to family routine; 3) family stress; 4) patient's disturbance level when not helped. From 70 answers (100.0 percent), 78.6 percent related participation in obsessive-compulsive behavior. Out of a total of 56 answers (100.0 percent), 78.6 percent indicated changes in family routine; 100.0 percent of the answers indicated family stress, and 83.3 percent indicate that the patient is disturbed when not helped.

O fenômeno da acomodação familiar em pais/mães de pacientes com transtorno obsessivo-compulsivo

Um dos fenômenos mais frequentes nas famílias de pacientes com Transtorno Obsessivo-Compulsivo é a acomodação familiar: participação nos rituais do paciente e modificações na rotina, contribuindo para o desencadeamento e a manutenção dos sintomas. Nesta pesquisa, verificou-se o grau de acomodação familiar apresentado por doze mães e dois pais, selecionados por meio da aplicação da Medida de Criticismo Percebido aos pacientes. Os familiares responderam à Escala de Acomodação Familiar. Os resultados foram analisados em torno de quatro temáticas: 1) participação nos rituais obsessivo-compulsivos do(a) paciente; 2) modificações na rotina familiar; 3) desgaste na família; 4) grau de perturbação do(a) paciente quando não atendido(a) em suas solicitações. De 70 respostas, 78,6 por cento afirmaram a participação nos rituais obsessivo-compulsivos; de 56 respostas, 78,6 por cento disseram haver modificações na rotina familiar; 100,0 por cento das respostas indicaram desgaste na família e 83,3 por cento mostraram que o paciente perturba os familiares quando não é atendido em suas solicitações.(AU)

One of the most frequent phenomena in the families of obsessive-compulsive disorder patients is Family Accommodation: participation in the patient's rituals, with modifications to the routine, which contributes to reinforcing and maintaining the symptoms. This study aimed to evaluate the level of Family Accommodation presented by 12 mothers and 2 fathers, selected from the Measure of Perceived Criticism applied to the patients. Results were analyzed according to four dimensions: 1) participation in patient's obsessive-compulsive rituals; 2) modifications to family routine; 3) family stress; 4) patient's disturbance level when not helped. From 70 answers (100.0 percent), 78.6 percent related participation in obsessive-compulsive behavior. Out of a total of 56 answers (100.0 percent), 78.6 percent indicated changes in family routine; 100.0 percent of the answers indicated family stress, and 83.3 percent indicate that the patient is disturbed when not helped.(AU)