This 1.7 million year old skull of Australopithecus boisei was discovered in 1969. Like all robust australopithecines it had huge cheek teeth which required massive muscles to function. Because the brain was small, there was only a small surface area of skull available for the attachment of the temporal muscle which moves the jaw when chewing. The large crest on the top of the skull increases the area of attachment for this huge muscle. The skull is the same species as the ‘Zinjanthropus’ skull discovered by Dr. Mary Leakey in 1959 at Olduvai Gorge.