Olorgesailie is a geological formation in East Africa, on the floor of the Eastern Rift Valley in southern Kenya, 67 kilometres (42 mi) southwest of Nairobi along the road to Lake Magadi.

[2] The artifacts were first discovered by the British geologist John Walter Gregory in 1919,[3][4] but it was not until 1943 that excavation began in earnest under the direction of Mary and Louis Leakey, with the assistance of paroled Italian prisoners of war.

Fossils of various animals have also been found, including those of extinct species of hippo, elephant, zebra, giraffe, and baboon, likely to have been butchered with the aid of the hand axes.

[10][11][12] Preservation of the Aechulean hand axe culture was made possible by heavy falls of alkaline ash from volcanoes near the site that were active at the time.

[13] In the 21 October 2020 issue of the journal Science Advances, an interdisciplinary team of scientists led by Richard Potts, director of the Human Origins Program at the Smithsonian's National Museum of Natural History, described the prolonged period of instability across the landscape in this part of Africa (now Kenya) that occurred at the same time humans in the region were undergoing a major behavioral and cultural shift in their evolution.

[14] Erosion at Olorgesailie, a hilly area full of sedimentary outcrops, had removed the geologic layers representing some 180,000 years of time at exactly the period of this evolutionary transition.