Doctoral Dissertation Improvement: Coevolutionary Models and the Evolution of the Anthropoid Honing Complex

两个特征，两足动物和较小的犬科动物，将人类和我们的化石祖先与其他猿类区分开来。在猴子和猿类中，犬齿通常相对较大，并参与咬合期间使犬齿变尖的功能复合体;退化的人类犬齿不锋利。功能复合体内的字符预计共同进化作为自然选择的结果，在非人类的灵长类动物中，该复合体的两个字符已被证明是物种之间的相关性，这表明该复合体的字符共同进化。在南方古猿属的早期人类中没有观察到类似的模式。因此，犬齿珩磨复合体提供了一个难得的机会来研究共同进化和溶解的功能复合体。性状的共同进化是不同过程的结果;例如，性状可能由于遗传相关而共同进化，遗传相关是由性状之间的多效性或遗传连锁产生的。在物种之间观察到的共同进化，在这种情况下是存在于物种内部的遗传关系的延伸。如果性状对选择的反应是独立的，那么在没有遗传相关性的情况下也会发生协同进化，这被称为选择性协变。该项目将确定珩磨复合体的特征是否共同进化，如果是，通过哪个过程。非人灵长类动物的遗传相关性需要在古人类进化过程中复合体的遗传解耦;然而，缺乏遗传相关性只需要改变选择压力的来源或强度来打破复合体。通过研究物种内和物种间的协变模式，将在现存的非人类类人猿中保持复合体在一起的过程将被阐明，这将是在人类中解耦复合体的过程。这个项目将调查犬齿减少的起源，这是人类进化的标志性特征之一。为了解决这个问题，灵长类动物齿系的形态将使用卡尺和牙弓测量进行量化。将对灵长类动物齿系的广泛样本进行测量，以确保样本在遗传学、体型和社会结构方面是广泛的。

Two features, bipedality and reduced canine size, distinguish humans and our fossil ancestors from other apes. In monkeys and apes the canines are typically relatively large and participate in a functional complex that sharpens the canines during occlusion; the reduced hominin canine is not sharpened. Characters within functional complexes are expected to coevolve as a result of natural selection and, among nonhuman anthropoid primates, two characters of this complex have been shown to be correlated among species, suggesting that characters of the complex do coevolve. A similar pattern is not observed in early hominins of the genus Australopithecus. Thus, the canine honing complex provides a rare opportunity to investigate the coevolution and dissolution of a functional complex. Character coevolution occurs as the result of different processes; for example, characters may coevolve because of genetic correlations, created by pleiotropy or genetic linkage, which exist among characters. Coevolution, observed among species, is in this case an extension of the genetic relationship that exists within species. Coevolution occurs in the absence of genetic correlations as well if characters respond independently to selection, which is termed selective covariation. This project will determine if characters of the honing complex coevolve and, if so, by which process. Genetic correlations in nonhuman primates would require a genetic decoupling of the complex during hominin evolution; however, the absence of genetic correlations would only require a change in the source or strength of selective pressures to break up the complex. By examining patterns of covariation, both within and among species, the process(es) that holds the complex together in extant nonhuman anthropoids will be elucidated as will be the process that decoupled the complex in hominins. This project will investigate the origin of canine reduction, one of the hallmark features of hominin evolution. To address this topic, the morphology of the primate dentition will be quantified using caliper- and photographic-based measurements. Measurements will be taken on a broad sample of primate dentitions to ensure that the sample is broad phylogenetically, in body size, and in social structure.