The brain’s connectome has a great impact on its function, as its structure affects the speed and efficiency of information transfer. As a highly energy-consuming organ, an efficient network structure is essential. A previous study has shown consistent overall brain connectivity across a large variety of species. This connectivity conservation was explained by a balance between inter and intra hemispheric connections, that is – spices with highly connected hemispheres appear to have weaker inter-hemisphere connections. This study examines this connectivity trade-off in the human brain using diffusion-based tractography and network analysis in the Human Connectome Project (970 subjects, 527 F). We explore the biological origins of this phenomenon, and heritability and effect on cognitive measures. The proportion of commissural fibers in the brain had a negative correlation to hemispheric efficiency, pointing to a trade-off between inner and inter hemispheric connectivity. Network hubs including anterior an...