Significance The subplate zone, a transient cellular compartment of the embryonic cerebrum, has expanded in size and complexity during primate evolution, culminating in humans. Here, the application of multiple methods, including labeling time and place of neuronal origin and subsequent changes in their positions in macaque monkey embryos, and the use of histo- and immunochemistry in human fetal cerebral tissue of comparable prenatal ages reveals extraordinary cellular dynamics and unexpected secondary displacement of neurons. These findings may have significance for understanding cortical development and evolution and may provide insight into the pathogenesis of cortical disorders, as well as hypoxic-ischemic lesions in preterm infants.