KNM-ER 732 A
Site: Koobi Fora, Kenya
Year of Discovery:
Discovered by: Richard Leakey and H. Mutua
Age: About 1.7 million years old
Species: Paranthropus boisei
KNM-ER 732, a partial cranium of a female Paranthropus boisei has many characteristic P. boisei features. Most notable is the forward placed root of the zygomatic arch, resulting in a wide flat face. This skull has a cranial capacity of 500 cubic centimeters, nearly identical to the 510 cubic centimeters of presumed male P. boisei KNM-ER 406. Yet the skull shows less robust facial features than KNM-ER 406; the face is less massive overall, and it lacks a sagittal crest. From this, scientists conclude that KNM-ER 732 represents a female of the Parathropus boisei species. This fossil provides clues as to the nature of sexual dimorphism in this early human species.