Best known Homo habilis
KNM-ER 1813 This fossil is one of the most complete skulls of this species, best known from the Turkana Basin (Kenya) and Olduvai Gorge (Tanzania) in East Africa. It has a cranial capacity of only 510 cubic centimeters, well below the 600 cubic centimeter cutoff that had been in place since the creation of the Homo habilis species name. It is also not much larger than the average for Australopithecus. Still, KNM-ER 1813 is similar to many of the accepted Homo habilis specimens from Olduvai Gorge, like OH 24. The similarities include overall size, smaller orbits, and sub-nasal prognathism (projection of the face below the nose). It is somewhat skewed on its left side, a result of the pressures the skull experienced during the fossilization process.
KNM ER 1813 was found a year after KNM-ER 1470 and led to the a debate over the exact nature of Homo. The discovery of KNM-ER 1470 solidified Homo habilis as a species, but the large cranium and big teeth of KNM-ER 1470 contrasted with the find of KNM-ER 1813. KNM-ER 1813 was an individual from the same time period in the same region, but with a small brain and diminutive teeth and face. The difference in size was not a result of KNM-ER 1813 being immature at the time of death; the third molars were fully erupted and showed evidence of wear, so she was probably a female who was fully mature at the time of her death.