The rhombic lip is a dorsal germinal zone that produces nearly 80% of all neurons in the human brain and assists in the production of all glutamatergic neurons in the cerebellum. In the mouse which has traditionally been used as a model organism, the rhombic lip is a transient structure and a dorsal stem cell zone that appears between embryonic days 12.5 and 17.5. While the mouse rhombic lip is molecularly compartmentalized, it lacks structural compartmentalization. The human rhombic lip on the other hand is long-lived and seen throughout gestation. It also exhibits substructure and is compartmentalized into a ventricular and subventricular zone. The extended duration of rhombic lip is a unique feature of human development and not seen in other model organisms including non-human primates like the macaque. This indicates that model organisms have limitations as they cannot fully recapitulate human development. Histological and immunohistochemical analyses of over 27 Dandy Walker Malformation (DWM) and Cerebellar Vermis Hypoplasia (CVH) samples suggest that rhombic lip disruption leads to cerebellar hypoplasia that disproportionately affects the posterior vermis. DWM and CVH are birth defects of the cerebellum that are diagnosed using ultrasound and MRI. Our histopathological analysis suggests that reduced proliferation and self-renewal of the rhombic lip progenitor pool leads to underdevelopment of the posterior cerebellum. These findings add to the understanding of the developmental pathogenesis of DWM, and underlines the need for further research of the human rhombic lip which can further improve our understanding of cerebellar brain defects.