Suchergebnisse

Abstract
Intimate partner violence (IPV) refers to physical, sexual and psychological violence. Here an evolutionary approach is used to compare risk factors for male-to-female IPV perpetration, analysing physical and sexual IPV separately. Two hypotheses based on sexual conflict theory have been applied to IPV perpetration, but they remain largely untested using empirical data: (a) men perpetrate IPV in response to a perceived threat to their paternity certainty; and (b) IPV is caused by men pursuing a higher fertility optima than their partners, either within marriage (reproductive coercion) or outside marriage (paternal disinvestment). Demographic Health Survey data from couples in 12 sub-Saharan African countries (n = 25,577) were used to test these evolutionary hypotheses, using multilevel models and controlling for potential social and environmental confounds. The results show that evolutionary theory provides important insight into different risk factors by IPV type. Indicators of paternity concern are associated with an increased risk of both physical and sexual IPV, indicators of paternal disinvestment are associated with an increased risk of physical IPV only, while reproductive coercion is not associated with either IPV type. The risk factors identified here correspond with proximate-level explanations for IPV perpetration, but an evolutionary interpretation explains why these particular factors may motivate IPV in certain contexts.

Intergenerational transfer of wealth has been proposed as playing a pivotal role in the evolution of human sibling relationships. Sibling rivalry is assumed to be more marked when offspring compete for limited heritable resources, which are crucial for reproductive success (e.g., land and livestock); whereas in the absence of heritable wealth, related siblings may cooperate. To date, comparative studies undertaken to support this evolutionary assumption have been confounded by other socioecological factors, which vary across populations, e.g., food sharing and intergroup conflict. In this article we explore effects of sibling competition and cooperation for agricultural resources, marriage, and reproduction in one contemporary Ethiopian agropastoralist society. Here recent changes in land tenure policy, altering transfers of land from parents to offspring, present a unique framework to test the importance of intergenerational transfers of wealth in driving sibling competition, while controlling for socioeconomic biases. In households where land is inherited, the number of elder brothers reduces a man's agricultural productivity, marriage, and reproductive success, as resources diminish and competition increases with each additional sibling. Where land is not inherited (for males receiving land directly from the government and all females) older siblings do not have a competitive effect and in some instances may be beneficial. This study has wider implications for the evolution of human family sizes. Recent changes in wealth transfers, which have driven sibling competition, may be contributing to an increased desire for smaller family sizes.

Summary.This study examines the reproductive success of men and women in rural Ethiopia as a function of their marital status, specifically by comparing polygamously and monogamously married individuals. In line with predictions from evolutionary theory, polygamy is beneficial to male reproductive success (i.e. producing larger numbers of surviving offspring). The success of polygamously married females depends on wife rank: the first wives of polygamous husbands do better than monogamously married women and much better than second or third wives. These effects are mirrored in child nutritional status: the children of second and third wives have lower weight for height. Due to potential, largely unmeasurable differences in marriageability (quality) between individuals, it was not possible to support a model of either resource-holding polygyny combined with female choice or female coercion into unwanted marriages. First wives of polygamously married men marry at a younger age and attract a higher brideprice, suggesting that both the males and females in the marriage are likely to be of higher quality (due to wealth, family status or some other factor such as beauty). Unions that end up monogamous are likely to be between slightly lower quality individuals; and second and third wives, who marry at the oldest ages and attract the lowest brideprice, may be 'making the best of a bad job'. The relatively long gap between first and second marriages may mean that first wives of highly marriageable males can enjoy considerable reproductive success before their husbands marry again.

As a species, we are currently experiencing dramatic shifts in our lifestyle, family structure, health, and global contact. Evolutionary Anthropology provides a powerful theoretical framework to study such changes, revealing how current environments and legacies of past selection shape human diversity. This book is the first major review of the emerging field of Applied Evolutionary Anthropology bringing together the work of an international group of evolutionary scientists, addressing many of the major public health and social issues of this century. Through a series of case studies that span both rural and urban situations in Africa, Asia, Europe and South America, each chapter addresses topics such as natural resource management, health service delivery, population growth and the emergence of new family structures, dietary, and co-operative behaviours. The research presented identifies the great, largely untapped, potential that Applied Evolutionary Anthropology holds to guide the design, implementation and evaluation of effective social and public health policy. This book will be of interest to policy-makers and applied researchers, along with academics and students across the biological and social sciences

Social support networks play a key role in human livelihood security, especially in vulnerable communities. Here we explore how evolutionary ideas of kin selection and intra-household resource competition can explain individual variation in daily-support network size and composition in a South-Central Ethiopian agricultural community. We consider both domestic and agricultural help across two generations with different large-wealth transfer norms that yield different contexts for sibling competition. For farmers who inherited land rights from family, first-borns were more likely to report daily support from parents and to have larger non-parental kin networks (n=176). Compared with other farmers, first-borns were also more likely to reciprocate their parents' support, and to help non-parental kin without reciprocity. For farmers who received land rights from the government (n=150), middle-born farmers reported more non-parental kin in their support networks compared with other farmers; non-reciprocal interactions were particularly common in both directions. This suggests a diversification of adult support network to non-parental kin, possibly in response to a long-term parental investment disadvantage of being middle-born sons. In all instances (with or without land inheritance), last-born farmers were the most disadvantaged in terms of kin support. Overall, we found that non-reciprocal interactions among farmers follow predictions of kin selection, and were more common for kin versus non-kin, and for close kin versus distant kin. Direct reciprocity explained a substantial part of the support received from kin, suggesting the importance of the combined effects of kin selection and reciprocity for investment from kin.

Abstract