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，且功能存在偏侧化特征，这提示二者之间存在关联。其他亲缘关系较近的灵长类动物（如黑猩猩）的大脑也呈现类似的不对称模式，但程度更弱，这表明在人属演化过程中，大脑的解剖学与功能不对称性均有所增强。本研究采用经典形态测量学、几何形态测量学以及定量遗传学技术，分析了黑猩猩与人类大脑不对称性的遗传力。分析过程中，我们将不对称性分为方向不对称性（directional asymmetry）与波动不对称性（fluctuating asymmetry, FA），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，在群体中多数个体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，其遗传力未达到显著水平；但当采用三维标志点构型（可反映不同脑皮层区域间的大小、位置及朝向差异）进行评估时，人类的方向不对称性则呈现边际显著的遗传力。此外，人类左右大脑半球间的遗传相关性显著低于黑猩猩，这提示环境因素对人类左右脑差异的影响相对更强。本研究同时发现，在两个物种的部分大脑皮层区域中，波动不对称性水平均存在显著的遗传力。这表明大脑对环境影响的响应能力（可反映神经可塑性）在两个物种中均存在遗传基础。本研究结果为人类及其近缘物种大脑不对称性与可塑性的演化潜力提供了新的启示。