Doctoral Dissertation Improvement: Causes of Sexual Size Dimorphism in Primates

本研究的目的是探讨灵长类动物性别大小二态性（SSD）的原因。SSD是指男性和女性在平均整体体型上存在差异。这些差异是有意义的，因为它们通常与灵长类动物的社会结构和群体组成有关，因此有助于推断已灭绝灵长类物种的自我组织方式。在推断灭绝种群时，了解SSD与这些其他因素之间的相关性是很重要的。该研究不同于早期的研究，在早期的研究中，跨物种的SSD指数和分类数据（例如，交配系统、饮食类型、底物类型）的分析与理论预测进行了比较。相反，定量模型被用来对连续数据的总体进行预测。预测是基于对应于可能产生SSD的机制的初始条件的——这些机制预测SSD与某些社会结构之间的高度相关性，而其他机制则不然。灵长类动物种群的数据将与模型预测进行比较，模型预测将考虑物种之间的亲缘程度，以确定哪些机制会在这些灵长类动物中产生SSD。这项研究有多个方面的意义。首先，它测试了另一种确定骨骼标本体型的技术的有效性。其次，介绍了一种测试特殊力对灵长类动物SSD影响的新技术。第三，它将确定影响特定灵长类动物群体以及整个灵长类动物的SSD的力量。最后，将祖先大小和分布参数的重建值与已知化石的值进行比较，进一步了解灵长类化石、灵长类祖先和现存灵长类之间的关系。

The purpose of this study is to investigate the causes of sexual size dimorphism (SSD) in primates. SSD is the presence of differences in mean overall body size between males and females. These differences are meaningful because they are often related to social structures and group compositions present in primates, and thus are useful in deducing the ways in which extinct primate species organized themselves. It is important to understand the strength of the correlation between SSD and these other factors when drawing inferences about extinct populations.The proposed study differs from earlier work in which analyses across species of SSD indices and categorical data (e.g., mating system, dietary type, substrate type) were compared to theoretical predictions. Instead, a quantitative model is used to generate predictions for populations of continuous data. Predictions are based on initial conditions that correspond to mechanisms that can potentially produce SSD - mechanisms that predict high correlation between SSD and certain social structures, and other mechanisms that do not. Data from primate populations will be compared to model predictions using analyses that take into account degree of relatedness between species to determine which mechanisms produce SSD in those primates.This study has multiple areas of significance. First, it tests the validity of an alternative technique for determining body size of skeletal specimens. Second, it introduces a new technique for testing the influence of particular forces on SSD in primates. Third, it will identify the forces that affect SSD within particular primate groups, as well as across the Order Primates. Finally, reconstructed values of ancestral size and distribution parameters can be compared with values of known fossils, furthering understanding of the relationships between fossil primates, ancestral primates, and living primates.