The evolution of despotic societies in mammals

社会等级制度限制了群体成员之间的冲突，通过控制他们对资源的获取;因此，等级制度中的社会等级几乎影响了个体达尔文适应性的各个方面。许多研究调查了群居物种中个体社会等级的原因和后果，但很少有人知道为什么有些动物社会比其他社会更有等级，特别是为什么社会等级在个体与等级的联系有多严格以及等级之间的差异有多陡峭方面有所不同。该项目旨在了解群体生活的哺乳动物中这种支配风格变化的进化起源，显示出从平等到专制社会的梯度，跨越多个尺度（个体，群体，种群和物种）。我们将检验三个主要假设，分别假定显性风格的个体差异（即，个体在社会等级中分配攻击性的频率和模式）代表稳定的、可遗传的行为综合征（H1），个体对生态或社会环境变化的灵活反应（H2），或对文化环境变化的社会习得反应，导致“平等主义”或“专制”文化（H3）。具体来说，我们将通过4个主要目标来研究优势风格的变化：1。在个体之间，以描述优势风格的个体差异，并测试其稳定性和遗传性（H1），使用来自三项长期研究的高分辨率行为数据，这些研究是关于野生查克玛狒狒（Papio ursinus）、山狮（Mandrillus sphinx）和斑点鬣狗（Crocuta crocuta）; 2.在社会群体内部和之间，通过将个人主导风格与群体主导风格联系起来，以测试它们是否反映了个体群体成员对生态，社会（H2）或文化（H3）环境变化的灵活反应，使用来自相同人群的建模和经验数据相结合。例如，个体可能会在自己的社会地位发生变化或处于阿尔法位置后调整其支配风格，以加强其在新等级中的地位，或者他们可能会在社会上学习和复制新群体成员的风格; 3.在种群和物种之间，提供哺乳动物社会中优势风格的进化历史的综合，并使用广泛的比较框架测试H1-3;和4.通过利用目标1-3和我们的研究人群提供的社会生态对比，研究为什么男性和女性的优势风格不同，性别之间的差异。最终，这个项目将揭示动物社会内部和之间社会不平等的进化起源。

Social hierarchies limit conflicts between the members of a group by regulating their access to resources; as a result, the social rank in the hierarchy affects nearly every aspect of an individual’s Darwinian fitness. Much research has investigated the causes and consequences of an individual’s social rank in group-living species, but little is known about why some animal societies are more hierarchical than others, and specifically why social hierarchies vary in how strictly individuals are tied to their rank and how steep the differences between ranks are. This project aims at understanding the evolutionary origins of such variation in dominance style in group-living mammals, showing a gradient from egalitarian to despotic societies, across multiple scales (individuals, groups, populations and species). We will test three main hypotheses, respectively positing that individual differences in dominance style (i.e., the frequency and pattern with which an individual distributes aggression across the social hierarchy) represent stable, heritable behavioural syndromes (H1), flexible individual responses to changes in the ecological or social environment (H2), or socially-learned responses to changes in the cultural environment, resulting in ‘egalitarian’ or ‘despotic’ cultures (H3). Specifically, we will investigate variations in dominance style through 4 main objectives: 1. across individuals, to characterize individual differences in dominance style and test their stability and heritability (H1), using high-resolution behavioural data from three long-term studies on wild chacma baboons (Papio ursinus), mandrills (Mandrillus sphinx) and spotted hyenas (Crocuta crocuta); 2. within and across social groups, by linking individual dominance styles to the group dominance style to test if they reflect flexible responses of individual group members to changes in the ecological, social (H2) or cultural (H3) environment, using a combination of modelling and empirical data from the same populations. Individuals may for instance adjust their dominance style following a change in their own social rank or in the alpha position to strengthen their position in the new hierarchy, or they may socially learn and copy the style of new group members; 3. across populations and species, to provide a synthesis of the evolutionary history of dominance style in mammalian societies and test H1-3 using a broad comparative framework ; and 4. between the sexes by capitalizing on Objectives 1-3 and on the socio-ecological contrasts offered by our study populations to investigate why male and female dominance styles differ. Ultimately, this project will shed new light on the evolutionary origins of social inequality within and across animal societies.