When fossil hunter Bernard Ngeneo came across the remains of this fossil, only the upper portion of the orbits were protruding from the ground. Excavation revealed one of the best preserved skulls of this time period, and one of the most striking early human fossils of any age.

KNM-ER 3733 represents a mature female of the early human species Homo erectus. The sex identification comes from a comparison of the anatomical features of her face with several other crania from Koobi Fora: KNM-ER 3883 (male), and KNM-WT 15000 (also male), found on the opposite side of Lake Turkana. The features of KNM-ER 3733 are markedly less robust. It's known to be an adult on the basis of the cranial sutures (which were fully closed), the extent of the wear on the teeth, and the eruption of the third molars before the individual's death.