Nearly two years have passed since Dr L.S.B. Leakey announced the first of a series of remarkable discoveries at Olduvai Gorge, Tanganyika. The great importance of this region as a palaeontological hunting ground has been appreciated since 1911 when, by chance, a German entomologist picked up a number of fossil bones which had been eroded on to the surface of the slopes of this East African Pleistocene canyon. Since 1931 Dr Leakey has made repeated visits to the Gorge where steadily he has been building up the evidence of an early stone-age cultural sequence.

In July, 1959, Dr and Mrs Leakey discovered a hominid skull which was lying partly exposed on the slopes, 22 ft. below the upper limit of Bed I, the lowest stratum of the Pleistocene sequence at Olduvai. Excavation of the site revealed that the skull was fragmented but almost complete and was lying on a living floor containing tools of a recognized culture (Oldowan) as well as waste flakes and unworked stones, all foreign to the site; in addition there were a number of broken and splintered bones of small animals which had apparently constituted part of the diet of the incumbents. Subsequently, a tibia and fibula were recovered from the same living floor. Dr Leakey named the skull Zinjanthropus boisei (PLATE x (a)). During 1960, excavations were started at a slightly lower level of Bed I and in December, 1960, Dr Leakey reported the discovery of a number of adult and juvenile bones of the hand and foot, two clavicles and some skull (parietal) fragments. This was rapidly followed by the important discovery of a juvenile mandible from the same level (PLATE XI). A number of stone artifacts of an Oldowan culture have also come to light from the juvenile site.