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

大脑解剖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的起源。扩大的球状前脑被认为通过启用新的认知、感觉和行为能力，从而打开新的生态位，促进了这些群体的进化成功。因此，几十年来，了解鸟类和哺乳动物大脑形状和大小进化变化的时间、速度和原因一直是进化生物学的主要焦点。但大脑扩张是有代价的：不仅大脑的新陈代谢成本很高，而且头部的其余部分也必须在物理上容纳和保护庞大的大脑。当大脑的大小增加时，对其他密切相关的解剖系统，如头骨、眼睛和颅肌的结构和功能的进化后果是什么？相反，这些结构对大脑的解剖学和进化性有什么影响？这个项目的目的是量化这些结构之间的权衡如何影响颅骨结构的形态多样性和宏观进化动力学。为了实现这一目标，我们将超越简单地量化特征之间的相关性，而是通过开发新的进化因果建模方法来分析特征之间的因果关系。我们将研究头部作为一个整体的进化，使用我的实验室首创的先进3D成像和形态测量方法对数百种现代和化石鸟类和哺乳动物的颅骨解剖进行量化。通过探究从宏观进化到微观进化的不同进化尺度的颅骨结构之间的权衡，以及发展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随时间影响多样性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.