Endocasts are important materials used for the study of human brain evolution,and allow examination of the external features of brain anatomy from the inside the cranium.Studies examining brain asymmetries in fossil hominids are usually limited to scoring of differences in hemisphere protrusion rostrally and caudally,or to comparing the width of the hemispheres.In the present study,using 3D laser scanning,we examined asymmetries of the hemisphere volumes and surface areas in the Zhoukoudain (ZKD) Homo erectus,dated to 0.4-0.8 Ma.Compared with modern endocasts,we found that the absolute hemisphere volumes and surface areas exhibited no significant asymmetries in the ZKD or in modern specimens.However,the relative hemisphere volumes against surface areas differed between the two groups.When comparing the relative sizes between the left and right hemispheres,the ZKD specimens exhibited a greater variation than in the modern humans;there were no differences in the two hemispheres in the ZKD specimens,while in the modern endocasts the left hemisphere was significantly greater than the right hemisphere.These data suggest that brain asymmetries originated from relative brain sizes rather than absolute brain volumes during human evolution.These anatomical changes are likely related to the origin of human brain lateralization. Endocasts are important materials used for the study of human brain evolution, and allow examination of the external features of brain anatomy from the inside of the cranium. Books examining brain asymmetries in fossil hominids are usually limited to scoring of differences in hemisphere protrusion rostrally and caudally, or to comparing with width of the hemispheres. the present study, using 3D laser scanning, we examined asymmetries of the hemisphere volumes and surface areas in the Zhoukoudain (ZKD) Homo erectus, dated to 0.4-0.8 Ma.Compared with modern endocasts, we found that the absolute hemisphere volumes and surface areas have no significant asymmetries in the ZKD or in modern specimens. Even, the relative hemisphere volumes against surface areas differed between the two groups .When comparing the relative sizes between the left and right hemispheres, the ZKD specimens exhibited a greater variation than in the modern humans; there were no differences in the two hemispheres in the ZK D specimens, while in the modern endocasts the left hemisphere was significantly greater than the right hemisphere. The data suggest that brain asymmetries originated from relative brain sizes rather than absolute brain volumes during human evolution. These anatomical changes are likely related to the origin of human brain lateralization.