Increased morphological asymmetry, evolvability and plasticity in human brain evolution
Increased morphological asymmetry, evolvability and plasticity in human brain evolution
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DOI：
10.1098/rspb.2013.0575
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发表时间：
2013-06-22
影响因子：
4.7
通讯作者：
Sherwood, Chet C.
中科院分区：
文献类型：
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作者：
Gomez-Robles, Aida;Hopkins, William D.;Sherwood, Chet C.
古人类脑进化的研究主要依赖于对颅骨化石颅内形态的评估。然而，颅腔模型只能显示脑外形态的一些一般特征，许多解剖细节很难或不可能检查。在这项研究中，我们使用几何形态测量技术来评估黑猩猩和人类体内磁共振成像扫描样本中大脑形态的种间和种内差异，特别强调对不对称变异的研究。研究表明，黑猩猩与人类在大脑形态上的差异主要是对称的；相比之下，物种之间的不对称变异具有连续性，人类的变异范围有所扩大。此外，不对称变异似乎不是种内异速缩放的结果，而对称变化在每个物种中表现出非常轻微的异速效应。我们的研究结果强调了人类进化中大脑进化的两个关键特性：首先，黑猩猩和人类的大脑（可能还有他们最后的共同祖先和相关物种）的进化没有很强的形态限制，因此使他们的大脑高度进化并对选择压力做出反应；其次，黑猩猩，尤其是人类的大脑表现出高度的波动不对称性，这表明了明显的发育可塑性。我们推断，这两个特征可能在人类认知进化中发挥作用。
The study of hominin brain evolution relies mostly on evaluation of the endocranial morphology of fossil skulls. However, only some general features of external brain morphology are evident from endocasts, and many anatomical details can be difficult or impossible to examine. In this study, we use geometric morphometric techniques to evaluate inter- and intraspecific differences in cerebral morphology in a sample of in vivo magnetic resonance imaging scans of chimpanzees and humans, with special emphasis on the study of asymmetric variation. Our study reveals that chimpanzee-human differences in cerebral morphology are mainly symmetric; by contrast, there is continuity in asymmetric variation between species, with humans showing an increased range of variation. Moreover, asymmetric variation does not appear to be the result of allometric scaling at intraspecific levels, whereas symmetric changes exhibit very slight allometric effects within each species. Our results emphasize two key properties of brain evolution in the hominine clade: first, evolution of chimpanzee and human brains (and probably their last common ancestor and related species) is not strongly morphologically constrained, thus making their brains highly evolvable and responsive to selective pressures; second, chimpanzee and, especially, human brains show high levels of fluctuating asymmetry indicative of pronounced developmental plasticity. We infer that these two characteristics can have a role in human cognitive evolution.