17 July 1959
On 17 July 1959, Palaeontologist Mary Leaky discovered on of the oldest hominid skulls in the Olduvai Gorge, in Northern Tanzania. At first she found several parts of the skull, and in the following few weeks, with her husband Louis Leakey, they uncovered more than 400 skull pieces. Originally they named it 'Zinjanthropus' (East African Man), but the skull was later renamed 'Australopithecus boisei'. The estimated age of the skull was 1.75 million years old. Leaky, who worked with her husband in Olduvai for many years, also developed a system for classifying stone tools in the area. She also discovered the Laetoli footprints, which is a line of hominin footprints preserved in volcanic ash. In 1960, Leaky became head of excavation at Olduvai, and after her husband's death, began to train her son, Richard, in the field.