Bailey Drew H, Hill Kim R, Walker Robert S
Department of Psychology, Carnegie Mellon University, Pittsburgh, PA 15213, USA
School of Human Evolution and Social Change, Arizona State University, Tempe, AZ 85287, USA.
Biol Lett. 2014 May;10(5):20140160. doi: 10.1098/rsbl.2014.0160.
Social norms that regulate reproductive and marital decisions generate impressive cross-cultural variation in the prevalence of kin marriages. In some societies, marriages among kin are the norm and this inbreeding creates intensive kinship networks concentrated within communities. In others, especially forager societies, most marriages are between more genealogically and geographically distant individuals, which generates a larger number of kin and affines of lesser relatedness in more extensive kinship networks spread out over multiple communities. Here, we investigate the fitness consequence of kin marriages across a sample of 46 small-scale societies (12,439 marriages). Results show that some non-forager societies (including horticulturalists, agriculturalists and pastoralists), but not foragers, have intensive kinship societies where fitness outcomes (measured as the number of surviving children in genealogies) peak at commonly high levels of spousal relatedness. By contrast, the extensive kinship systems of foragers have worse fitness outcomes at high levels of spousal relatedness. Overall, societies with greater levels of inbreeding showed a more positive relationship between fitness and spousal relatedness.
规范生育和婚姻决策的社会规范在近亲婚姻的发生率上产生了令人瞩目的跨文化差异。在一些社会中，近亲结婚是常态，这种近亲繁殖形成了集中在社区内的密集亲属网络。在其他社会，尤其是觅食社会，大多数婚姻发生在血缘关系和地理距离更远的个体之间，这在分布于多个社区的更广泛亲属网络中产生了大量亲缘关系较浅的亲属和姻亲。在此，我们对46个小规模社会（12439例婚姻）的样本进行研究，以探讨近亲婚姻对生育适应性的影响。结果表明，一些非觅食社会（包括园艺社会、农业社会和畜牧社会），而非觅食社会，拥有密集亲属社会，在这些社会中，生育适应性结果（以族谱中存活子女的数量衡量）在配偶亲缘关系通常较高的水平时达到峰值。相比之下，觅食社会的广泛亲属系统在配偶亲缘关系较高时生育适应性结果较差。总体而言，近亲繁殖程度较高的社会在生育适应性和配偶亲缘关系之间呈现出更积极的关系。
