Issues in Hominin Brain Evolution
The anatomy of the brain is rather complex. At the microscopic level, the brain is composed of billions of specialized cells called neurons (nerve cells), which communicate with one another to form functional networks (see Appendix A). At the visible level, the cerebral cortex , the surface of the brain composed of neuron cell bodies, is divided into a complex pattern of grooves and ridges called sulci (sing.,sulcus ) and gyri (sing., sulcus ), some of which can be used as landmarks to divide the brain into functional regions. Two of the major parts of the brain are the cerebellum and the cerebrum . The cerebellum, or “little brain,” sits tucked under the cerebrum, and is important in the control of balance, posture, and voluntary movements. It also plays an important role in “higher” cognitive functions that were once thought to be solely under the control of the cerebrum. The cerebrum itself, which is where most complex cognitive functions are located, is the part of the brain that most people recognize as being “the brain.” In humans and other primates, the cerebrum forms most of the brain’s volume, and it is generally thought that the expansion of the cerebrum in human evolution has occurred as a direct result of selection for more complex forms of behavior.
人族的大脑进化历程
大脑的解剖结构是非常复杂的。在微观层面，脑部是由数以十亿计的被称为神经元（神经细胞）的特殊分化细胞组成的，互相之间形成连结构成功能性网络（见附录A）。在可视层面，大脑皮层，大脑的表面由神经元细胞体组成，被一种复杂的由凹和嵴区分成特定区域，这些凹和嵴通常被称为脑沟和脑回，其中的一些可以作为大脑皮层上的解剖标志来区分特定功能区域。其中两个主要部分就是小脑和大脑（其实这个词有时被翻成端脑）。小脑，或者“小的大脑”，盘缩在大脑的后下部，是控制身体平衡、姿势和随意运动的重要中枢。同时，它也是“高级”认知功能的重要组分，这个功能曾经一度被认为是大脑单独控制的。大脑本身，就是最复杂认知功能的所在地，也是大多时候被人们认为的“脑子”。在人类和其他灵长类身上，大脑占据了脑容量中的绝大部分，并且通常认为在人类进化中大脑的扩展直接导致了更复杂行为的选择性进化。
Recent technological advances have provided us with some extraordinary
tools for examining the brain, but the study of the evolution of brain structure and function, or paleoneurology , remains for the most part dependent on the study of endocasts. Endocasts are impressions of the interior part of the cranium, from which we can make inferences about the size and structure of the brain (Tobias, 1971）（ Figure 15.1 on page 449). Scientists make endocasts from fossil skulls, or in rare cases endocasts form naturally during fossilization (see Chapter 11 ). Unfortunately, the brain is separated from the inside of the cranium by several protective tissue layers and cerebrospinal fluid, so endocasts are inevitably a poor reflection of the brain’s anatomy. Nonetheless, they provide us with the only source of direct information we have about the brain structure of extinct species.
最近的技术进步提供给我们许多优秀的工具来检查大脑，但是研究脑部进化的结构和功能，或者说古神经科学，仍然重度依靠对颅腔模型的研究。颅腔模型是头盖骨的内部的模子，通过这种模型我们能够推断脑部的尺寸和结构。科学家从头骨化石制作颅腔模型，或者那些很稀少的案例中自然化石化形成的颅腔模型（见章节11）。不幸的是，脑被从内部
以几层保护性的组织层和脑脊液所分隔，所以颅腔模型就不可避免的只能反映出很少的脑部解剖结构特征。尽管如此，它们仍然是我们能够得到的唯一直接反应曾经存在的灭绝物种脑部信息的来源。
Most of the important questions concerning hominin brain evolution address
ways in which the human brain is different from the brains of other primates and mammals. But there are many ways in which our brains are similar to those of other mammals. We use the same neurochemicals, share a basic microscopic and macroscopic architecture, and have some basic sulci and gyri around which functional regions are organized.
大多数有关人族脑部进化的重要问题聚焦在人类的脑是如何不同于其他灵长类和哺乳类的脑的。但是，我们的脑其实和其他这些哺乳类有许多相似点。我们使用相同的神经化学递质，分享着一套基础微观和宏观脑部结构，以及一些组成功能区域的基本的脑沟和脑回。

Although Neandertal and modern human brains are similar in size, their overall shapes are quite different. Modern humans have brains that are much more globe-shaped than Neandertal archaic Homo sapiens brains (Lieberman et al., 2002; Bruner, 2004). This “globularization” may reflect in particular changes in the parietal lobes and the region around the border of the temporal and parietal lobes. Studies of endocasts of very young Neandertal and human children suggest that this difference in shape emerges very early, within the first year of life (Gunz et al., 2010). The globularization of the human brain thus appears to reflect a unique pattern of brain growth and development within primates, which may be distinct from changes in size.
尽管尼安德特人和现代人的脑近乎相同大小，他们的整体形状却十分不同。相比于尼安德特人和古代智人,现代人的脑部更接近球形。这种“球形化”可能反映着脑顶叶以及颞叶和顶叶周边的区域的特殊改变。通过对幼年尼安德特人和现代人儿童的颅腔模型的研究发现，这种差异在童年早起就已出现。因此现代人的脑部球形化可能反映出了灵长类脑部发育和发展的一种特殊模式，这可能和大小的改变是不同的。
Brain size increase and increased encephalization have characterized hominin evolution over the past 3 to 4 million years ( Figure 15.6 ). These trends have become more marked over the past 2 million years, as absolute brain size has nearly tripled. During the past 2 million years, increases in brain size have outpaced increases in body size, thus leading to increasingly encephalized hominins. Although brain size and encephalization are not everything, expanding brain size in the hominin lineage clearly reflects an adaptation, given how “expensive” brain tissue is (see Insights and Advances: The Ten-Percent Myth: Evolution and Energy on page 455).
脑部大小的增加和脑部功能的加强特征化了300到400万年前的的人类进化（图片15.6）。这些趋势在200万年前变得更加显著，其绝对脑部大小增大了原来的3倍。在200万年前，脑部的增长超过了身体的增长，因此出现了脑部发达的人类。尽管脑部大小和功能发展不是一切，人族增大的大脑清晰的反映了一种适应性，这些脑组织是如此“昂贵”。（请看视野和进步：百分之十的神话：进化和能量455页）。

鼓励汉化

然而世界终归鼠国“

姿势帖留名

看图还以为是要讨论xcom2，没想到居然是学术文章，太高深
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