Center for the Advanced Study of Hominid Paleobiology, Department of Anthropology, The George Washington University, Washington, DC 20052, USA.
J Hum Evol. 2010 Apr;58(4):281-92. doi: 10.1016/j.jhevol.2009.11.011. Epub 2010 Feb 21.
It has been argued that changes in the relative sizes of visual system structures predated an increase in brain size and provide evidence of brain reorganization in hominins. However, data about the volume and anatomical limits of visual brain structures in the extant taxa phylogenetically closest to humans-the apes-remain scarce, thus complicating tests of hypotheses about evolutionary changes. Here, we analyze new volumetric data for the primary visual cortex and the lateral geniculate nucleus to determine whether or not the human brain departs from allometrically-expected patterns of brain organization. Primary visual cortex volumes were compared to lunate sulcus position in apes to investigate whether or not inferences about brain reorganization made from fossil hominin endocasts are reliable in this context. In contrast to previous studies, in which all species were relatively poorly sampled, the current study attempted to evaluate the degree of intraspecific variability by including numerous hominoid individuals (particularly Pan troglodytes and Homo sapiens). In addition, we present and compare volumetric data from three new hominoid species-Pan paniscus, Pongo pygmaeus, and Symphalangus syndactylus. These new data demonstrate that hominoid visual brain structure volumes vary more than previously appreciated. In addition, humans have relatively reduced primary visual cortex and lateral geniculate nucleus volumes as compared to allometric predictions from other hominoids. These results suggest that inferences about the position of the lunate sulcus on fossil endocasts may provide information about brain organization.
有人认为，视觉系统结构的相对大小的变化早于大脑体积的增加，并为人类同源物的大脑重组提供了证据。然而，关于与人类亲缘关系最密切的现存分类群（即猿类）的视觉大脑结构的体积和解剖学限制的数据仍然很少，这使得关于进化变化的假设的检验变得复杂。在这里，我们分析了初级视觉皮层和外侧膝状体的新体积数据，以确定人类大脑是否偏离了与生长相关的大脑组织模式。我们将初级视觉皮层的体积与月状沟的位置进行比较，以调查从化石人类内颅骨推断的大脑重组是否在这种情况下可靠。与之前的研究相比，在这些研究中，所有物种的样本都相对较少，目前的研究试图通过包括许多人科动物个体（特别是黑猩猩和智人）来评估种内变异的程度。此外，我们还介绍并比较了来自三个新的人科物种（黑猩猩、猩猩和指猴）的体积数据。这些新数据表明，人科动物的视觉大脑结构体积的变化比以前认识到的要大。此外，与其他人类同源物的生长相关预测相比，人类的初级视觉皮层和外侧膝状体体积相对较小。这些结果表明，关于化石内颅骨上月状沟位置的推断可能提供关于大脑组织的信息。
