近日,一项研究发现,当忠实的女性开始选择良好的供应者作为配偶的时候,配偶结合就在人类进化中取代了乱交。由于灵长类群体通常建立支配地位驱动的等级结构,让交配的特权仅限于少数高等级的雄性,进化生物学家努力解释配偶结合以及这种核心家庭结构如何在人类中间起源。相关研究论文“Human origins and the transition from promiscuity to pair-bonding,”刊登在了近日的国际杂志PNAS上。
利用简单的数学模型,Sergey Gavrilets揭示出了最常被提出的人类配偶结合的理论在生物学上是不切实际的。然后,把女性选择和忠诚度的进化等因素结合进来,这位科研人员设计出了一个模型表明了配偶结合如何代表了一种关键的适应,强调了人类进化的独特性。
这组作者提出,地位低的男性很可能通过把重点几乎全部放在成为最佳的供应者上,从而开始吸引配偶,这种策略有增强女性生育力并支持他们的后代存活的额外收益。在进化的时间尺度上,该模型表明,除了地位最高的男性,所有其他男性将会转变成向进化出高忠诚感的女性供应资源。这位作者说,这些发现表明女性的选择在人类进化中是关键因素,他们还提出,未来关于社会行为的研究应该明确地考虑到影响社会互动动态的个体之间的差异。(生物谷Bioon.com)
doi:10.1073/pnas.1200717109
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Human origins and the transition from promiscuity to pair-bonding
Sergey Gavrilets1
A crucial step in recent theories of human origins is the emergence of strong pair-bonding between males and females accompanied by a dramatic reduction in the male-to-male conflict over mating and an increased investment in offspring. How such a transition from promiscuity to pair-bonding could be achieved is puzzling. Many species would, indeed, be much better off evolutionarily if the effort spent on male competition over mating was redirected to increasing female fertility or survivorship of offspring. Males, however, are locked in a “social dilemma,” where shifting one’s effort from “appropriation” to “production” would give an advantage to free-riding competitors and therefore, should not happen. Here, I first consider simple models for four prominent scenarios of the human transition to pair-bonding: communal care, mate guarding, food for mating, and mate provisioning. I show that the transition is not feasible under biologically relevant conditions in any of these models. Then, I show that the transition can happen if one accounts for male heterogeneity, assortative pair formation, and evolution of female choice and faithfulness. This process is started when low-ranked males begin using an alternative strategy of female provisioning. At the end, except for the top-ranked individuals, males invest exclusively in provisioning females who have evolved very high fidelity to their mates. My results point to the crucial importance of female choice and emphasize the need for incorporating between-individual variation in theoretical and empirical studies of social dilemmas and behaviors.