One outstanding phenotypic character in Homo is its brain evolution. Pagel (Morphology, shape and phylogeny, CRC Press, Boca Raton, 2002) performed a phylogenetic analysis of the evolution of cranial capacity (as a surrogate of brain size) in fossil hominins, finding evidence for gradual evolutionary change with accelerating rate. Since Pagel’s pioneering investigation, the hominin fossil record expanded backward in time, new species were added to our family tree, different phylogenetic hypotheses were advanced, and new phylogenetic comparative methods became available. Therefore, we feel it is timely to repeat and expand upon Pagel’s seminal paper by including such material and applying novel methodologies. We fitted several evolutionary models to the endocranial volume (ECV) for 21 fossil hominins (including Pagel’s original analyses) and estimated phylogenetic signal using different approaches, while accounting for phylogenetic uncertainty. We then applied the phylogenetic signal-representation curve to the data to look for non-stationarity (discontinuities, rate shifts, or presence of different evolutionary patterns in different parts of the phylogeny) in brain size evolution. Our analyses show that, in principle, Pagel’s findings are robust to the addition of new data and phylogenetic uncertainty and confirm both the strong phylogenetic signal in brain size and acceleration of ECV evolutionary rates towards the present. However, non-stationarity was also detected in about 11% of the simulations, with two significant evolutionary discontinuities occurring close to the origin of the H. sapiens lineage (H. sapiens, H. neanderthalensis, H. heidelbergensis and H. antecessor) and along the phyletic line leading to H. floresiensis. This study calls upon further investigation of these important moments in Homo evolution, in order to understand the processes underling each of these shifts in brain size evolutionary regimes.

中文翻译：

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化石人豆脑大小演变中系统发生非平稳性的多个组成部分。

同源人一个杰出的表型特征是它的大脑进化。Pagel（形态学，形状和系统发育，CRC Press，Boca Raton，2002）对人化石中颅骨能力的演变（作为大脑大小的替代物）进行了系统发育分析，发现了随着进化速率的逐渐演变而变化的证据。自Pagel的开创性研究以来，人化石的记录随着时间​​的推移向后扩展，将新物种添加到我们的家谱中，提出了不同的系统发育假设，并提供了新的系统发育比较方法。因此，我们认为通过包含此类材料并应用新颖的方法，可以适当地重复和扩展Pagel的开创性论文。我们对21种化石人类素的颅内体积（ECV）拟合了几种进化模型（包括Pagel的原始分析），并使用不同的方法估算了系统发生信号，同时考虑了系统发生的不确定性。然后，我们将系统发育信号表示曲线应用于数据，以寻找大脑大小进化中的非平稳性（不连续性，速率变化或系统进化的不同部分中不同进化模式的存在）。我们的分析表明，从原则上讲，Pagel的发现对增加新数据和系统发育不确定性是可靠的，并证实了脑部大小上的强大系统发育信号和目前ECV进化速率的加速。但是，在大约11％的模拟中也检测到非平稳性，智人血统（智人，尼安德特人血统，海德堡血统和前人血统）并沿着导致弗洛瑞斯血统的种系。这项研究呼吁进一步研究人进化中的这些重要时刻，以了解大脑大小进化机制中每个这些转变背后的过程。