The Evolution of Sex Differences in Mammalian Social Life Histories

理解为什么长寿的群居哺乳动物的社会行为和生活史在两性之间存在差异，有时甚至达到极端程度，是生物学、医学和社会科学的一个关键目标。我们认为，两性之间在一生中如何与相关个体互动的差异是推动社会行为和生活史中性别差异进化的主要力量。在群居物种中，有亲缘关系的个体（亲属）通常生活在紧密联系的家庭群体中，个体可以通过其行为（合作和竞争）和生殖决策（如果一个个体繁殖，它将使用可能对亲属的生存和生殖成功产生负面影响的资源）来影响其亲属的生存和生殖成功。亲属之间的这种相互作用是一种强大的进化力量，个体通过提高亲属的存活率和繁殖成功率而获得间接利益（通过与亲属共享基因）。例如，亲缘选择有利于提高亲缘繁殖成功率的个体策略，即使这是以个体的生存和繁殖成功为代价的。亲缘选择影响进化的机会取决于相关个体如何以及何时相互作用。我们的试点工作表明，在许多物种中，由于分散和交配的模式，雄性和雌性在其一生中经历了非常不同的本地亲缘关系模式（亲缘关系动力学）。例如，对于一些物种，如虎鲸，随着年龄的增长，雌性与当地群体的关系越来越密切，而雄性则相反，变得越来越不密切。我们假设亲属关系动态中的性别差异将是推动(i)社会行为和（ii）生活史中性别差异演变的主要力量。我们将利用理论建模和经验数据分析相结合的方法，确定亲属关系动态在推动社会行为和生活史进化中的性别差异演变中的作用。我们将发展亲属关系动态的一般理论，并开发新的模型来预测亲属关系动态的模式及其对男性和女性社会生活史演变的影响。我们的模型将预测社会群体中帮助和伤害的模式，包括行为特征（合作和冲突）和生殖特征（例如第一次或最后一次生育的年龄）。我们将为我们的新理论的行为预测提供第一个测试，通过收集使用无人驾驶飞行器（无人机）帮助（例如照看婴儿和分享食物）和伤害（攻击）常驻虎鲸的模式的新数据。常驻虎鲸非常适合测试模型的行为预测——它们在亲缘关系动态上存在极端的性别差异，在生活史上也存在无法解释的性别差异。我们将通过比较社会性哺乳动物的亲属关系动态模式和生活史进化中的性别差异（例如，生长模式、首次繁殖年龄、最后繁殖年龄、生殖投资和寿命）来测试理论框架的生活史预测，这将使我们能够确定亲属关系动态在推动生活史进化和两性生活史差异中的作用。

Understanding why social behaviour and life histories have diverged between the sexes in long-lived social mammals, sometimes to an extreme degree, is a key objective in the biological, medical and social sciences. We propose that differences between the sexes in how males and females interact with related individuals across the lifespan are a major force driving the evolution of sex differences in both social behaviour and life history. In social species related individuals (kin) often live together in close knit family groups and individuals can influence the survival and reproductive success of their relatives both by their behaviour (cooperative and competitive) and reproductive decisions (if an individual reproduces it will use resources that may negatively impact on the survival and reproductive success of kin). Such interactions between kin are a strong evolutionary force, with individuals gaining indirect benefits (through the genes they share with relatives) by increasing the survival and reproductive success of their kin. For example, kin selection can favour individual strategies that increase the reproductive success of kin, even if this comes at a cost to an individual's survival and reproductive success. The opportunity for evolution to be shaped by kin selection is dependent on how and when related individuals interact. Our pilot work suggests that in many species males and females experience very different patterns of local relatedness across their lifespans (kinship dynamics) due to patterns of dispersal and mating. For example, for some species such as killer whales, females become more related to their local group with age whereas males, in contrast, become less related. We hypothesise that sex differences in kinship dynamics will be a major force driving the evolution of sex differences in both (i) social behaviour and (ii) life history. We will determine the role of kinship dynamics in driving the evolution of sex differences in social behaviour and life history evolution using a combination of theoretical modelling and empirical data analysis. We will develop a general theory of kinship dynamics and develop new models to predict both the patterns of kinship dynamics and their consequences for the evolution of social life histories in both males and females. Our model will make predictions for patterns of helping and harming in social groups including both behavioural traits (cooperation and conflict) and reproductive traits (e.g. age at first or last reproduction). We will provide the first test of the behavioural predictions of our new theory by collecting new data on patterns of helping (e.g. babysitting and food sharing) and harming (aggression) in resident killer whales using unmanned aerial vehicles (drones). Resident killer whales are ideally suited to testing the behavioural predictions of the model - they have extreme sex differences in kinship dynamics and have unexplained sex differences in life history. We will test the life history predictions of the theoretical framework by comparing patterns of kinship dynamics and sex differences in life history evolution (e.g. patterns of growth, age at first reproduction, age at last reproduction, reproductive investment and longevity) across social mammals which will allow us to determine the role of kinship dynamics in driving life history evolution and the divergence of life histories between the sexes.