Polyandry : in human societies and the animal kingdom

Polyandrous mating systems are found in both animals and humans. This paper focuses on the different hypotheses posed in literature as an explanation of polyandry. In this paper I aim to discover to which extent human polyandrous mating societies differ from polyandrous mating populations of other species in the animal kingdom. I emphasise evolutionary aspects. Polyandry has, in literature, a wide range of definitions. In this report polyandry is classified in two groups, narrow sense and broad sense polyandry. In human (narrow sense) polyandrous societies one female marries several brothers. This system is thought to prevent landfragmentation, population growth and fragmentation of other properties needed in harsh ecological conditions. Striking are the similarities between the functions ascribed to human polyandry and other narrow sense polyandrous species in the animal kingdom, as for example the dunnock and challitnchids. In broad sense polyandry multiple mating by the female is central. In contrast to narrow sense polyandry a pair bond between partners in not required and males do not mate solely with one female. Broad sense polyandry hypotheses are often based on genetic fitness benefits of multiple mating by females. Although no genetic fitness benefits of narrow sense polyandry are given in literature, I propose that for example the genetic diversity hypothesis might apply to narrow sense polyandrous species. The inbreeding avoidance hypothesis and sperm competition may possibly also give insight in why some species mate narrow sense polyandrously. At last, factors affecting the stability of narrow sense polyandry are explored. These factors are, stability of environment, economic diversity, and number, age and relatedness of male partners.