Data from: The heritability of chimpanzee and human brain asymmetry

Human brains are markedly asymmetric in structure and lateralized in function, which suggests a relationship between these two properties. The brains of other closely related primates, such as chimpanzees, show similar patterns of asymmetry, but to a lesser degree, indicating an increase in anatomical and functional asymmetry during hominin evolution. We analysed the heritability of cerebral asymmetry in chimpanzees and humans using classic morphometrics, geometric morphometrics, and quantitative genetic techniques. In our analyses, we separated directional asymmetry and fluctuating asymmetry (FA), which is indicative of environmental influences during development. We show that directional patterns of asymmetry, those that are consistently present in most individuals in a population, do not have significant heritability when measured through simple linear metrics, but they have marginally significant heritability in humans when assessed through three-dimensional configurations of landmarks that reflect variation in the size, position, and orientation of different cortical regions with respect to each other. Furthermore, genetic correlations between left and right hemispheres are substantially lower in humans than in chimpanzees, which points to a relatively stronger environmental influence on left–right differences in humans. We also show that the level of FA has significant heritability in both species in some regions of the cerebral cortex. This suggests that brain responsiveness to environmental influences, which may reflect neural plasticity, has genetic bases in both species. These results have implications for the evolvability of brain asymmetry and plasticity among humans and our close relatives.

人类大脑在结构上呈现显著不对称性，功能上表现出偏侧化特征，这提示这两种特性之间存在关联。与人类亲缘关系较近的其他灵长类动物，如黑猩猩，其大脑也存在类似的不对称模式，但程度更低，这表明在人科动物的演化过程中，解剖学与功能不对称性均有所增强。本研究借助经典形态测量学（classic morphometrics）、几何形态测量学（geometric morphometrics）与定量遗传学技术（quantitative genetic techniques），分析了黑猩猩与人类的大脑不对称性遗传力。在分析过程中，我们将方向不对称性（directional asymmetry）与波动不对称性（fluctuating asymmetry, FA）进行了区分，其中波动不对称性可反映发育过程中的环境影响。研究结果显示，群体内多数个体均普遍存在的方向不对称模式，若通过简单线性指标进行测量，其遗传力并不显著；但当通过三维标志点构型（three-dimensional configurations of landmarks）进行评估时，该构型可反映不同大脑皮层区域的大小、位置及相对朝向的变异，人类的方向不对称性则表现出边际显著的遗传力。此外，人类左右大脑半球间的遗传相关性显著低于黑猩猩，这提示环境对人类左右侧差异的影响相对更强。我们还发现，在两个物种的部分大脑皮层区域中，波动不对称性水平均具有显著的遗传力。这表明，大脑对环境影响的响应能力（可反映神经可塑性（neural plasticity））在两个物种中均存在遗传基础。本研究结果对人类及其近缘物种的大脑不对称性与可塑性的可进化性（evolvability）具有启示意义。