Ponting Chris, Jackson Andrew P
MRC Functional Genetics, University of Oxford, Department of Human Anatomy and Genetics, South Parks Road, Oxford OX1 3QX, UK.
Curr Opin Genet Dev. 2005 Jun;15(3):241-8. doi: 10.1016/j.gde.2005.04.009.
Brain size, in relation to body size, has varied markedly during the evolution of mammals. In particular, a large cerebral cortex is a feature that distinguishes humans from our fellow primates. Such anatomical changes must have a basis in genetic alterations, but the molecular processes involved have yet to be defined. However, recent advances from the cloning of two human disease genes promise to make inroads in this important area. Microcephalin (MCPH1) and Abnormal spindle-like microcephaly associated (ASPM) are genes mutated in primary microcephaly, a human neurodevelopmental disorder. In this 'atavistic' condition, brain size is reduced in volume to a size comparable with that of early hominids. Hence, it has been proposed that these genes evolved adaptively with increasing primate brain size. Subsequent studies have lent weight to this hypothesis by showing that both genes have undergone positive selection during great ape evolution. Further functional characterisation of their proteins will contribute to an understanding of the molecular and evolutionary processes that have determined human brain size.
在哺乳动物的进化过程中，相对于身体大小而言，脑容量发生了显著变化。特别是，大脑皮层较大是人类区别于其他灵长类动物的一个特征。这种解剖学上的变化必然有遗传改变作为基础，但其中涉及的分子过程尚未明确。然而，最近克隆出两个人类疾病基因所取得的进展有望在这个重要领域取得突破。小头畸形基因（MCPH1）和异常纺锤样小头畸形相关基因（ASPM）是在原发性小头畸形（一种人类神经发育障碍）中发生突变的基因。在这种“返祖”情况下，脑容量缩小到与早期原始人类相当的大小。因此，有人提出这些基因随着灵长类动物脑容量的增加而适应性进化。随后的研究通过表明这两个基因在类人猿进化过程中都经历了正选择，为这一假设提供了支持。对其蛋白质的进一步功能表征将有助于理解决定人类脑容量的分子和进化过程。
