 Compared to the modern human and the "Homo ergaster" the "A. boisei" had a cranial capacity of 510 cc, a much smaller brain then modern humans who have a cranial capacity of 1200-1400 cc.He had striking robusticity, projecting glabella, and a well developed sagittal crest.There are feature differences of the sagittal crest in the KNM-ER 406 and the robust male gorillas and chimpanzees.