Figure 1.

Timeline of gyrification in human. Stages 1 and 2 are delineated by GW 31-32. There is a progressive lack of conservation in cortical folding patterns toward the final stages of gyrification, as minor developmental changes in gyri and sulci become increasingly specialized to species and, ultimately, susceptible to local environmental and experiential variations. 3D reconstructions of fetal human brains from Barnette et al. (2009). Figure follows Sawada et al. (2012b).