The Consequences of Encephalization: Testing Trade-offs in Cranial Evolution

大脑解剖学的进化变化是一些最重要的进化转变的基础，包括鸟类，胎盘哺乳动物和原始人类的起源。增大的球状前脑被认为通过启用新的认知、感觉和行为技能，从而解锁新的生态位，促进了这些群体的进化成功。出于这个原因，了解鸟类和哺乳动物大脑形状和大小进化变化的时间，速度和原因几十年来一直是进化生物学的主要焦点。但是大脑的扩张是有代价的：不仅大脑的代谢成本很高，而且头部的其他部分也必须在身体上容纳和保护大大脑。当大脑体积增大时，其他密切相关的解剖系统（如颅骨、眼睛和颅肌）的结构和功能会发生什么样的进化后果？反过来说，这些结构对大脑的解剖结构和进化能力有什么影响呢？这个项目的目的是量化颅结构的形态多样性和宏观进化动力学如何受到这些结构之间的权衡的影响。为了实现这一目标，我们将超越简单地量化性状之间的相关性，而是通过开发新的进化因果建模方法来分析性状之间的因果相互作用。我们将研究头部的演化作为一个整体，使用先进的3D成像和形态测量方法在我的实验室开创了量化的现代和化石鸟类和哺乳动物的颅骨解剖数百。通过询问从宏观进化到微观进化的不同尺度的颅骨结构之间的权衡，并开发新的系统发育比较方法，我们将为理解复杂性状之间的相互作用如何影响多样性随时间的进化提供新的证据和工具。

Evolutionary changes in brain anatomy underlie some of the most significant evolutionary transitions, including the origins of birds, placental mammals, and hominids. Enlarged, globular forebrains are thought to have facilitated the evolutionary success of these groups by enabling new cognitive, sensory, and behavioural repertoires, thereby unlocking new ecological niches. For this reason, understanding the timing, rate, and cause of evolutionary changes in brain shape and size in birds and mammals has been a major focus in evolutionary biology for decades. But brain expansion comes at a cost: not only is the brain metabolically expensive, but the rest of the head must also physically accommodate and protect the large brain. When brain size increases, what are the evolutionary consequences for the structure and function of other closely associated anatomical systems such as the skull, eye, and cranial muscles? Conversely, what influence do these structures exert on the brain's anatomy and evolvability? The aim of this project is to quantify how the morphological diversity and macroevolutionary dynamics of cranial structures have been influenced by the tradeoffs among these structures. To achieve this goal, we will go beyond simply quantifying correlations between traits and instead analyse the cause-and-effect interactions between traits by developing new evolutionary causal modelling methods. We will examine the evolution of the head as an integrated whole, quantifying the cranial anatomy of hundreds of modern and fossil birds and mammals using advanced 3D imaging and morphometric methods pioneered in my lab. By interrogating the trade-offs among cranial structures across scales of evolution, from macroevolutionary to microevolutionary, and developing new phylogenetic comparative methods, we will provide new evidence and tools for understanding how the interactions among complex traits affect the evolution of diversity through time.