Located on the southeastern edge of the Great Rift Valley and on Lake Elmenteita, Kariandusi is an African Early Stone Age site dating to approximately 1 million years ago.

Due to his success, St. John's awarded Leakey a research grant for his first East African Archaeological Expedition.

At the time that Kariandusi was in use, 1 million years ago, Homo erectus was in the eastern African Rift Valley.

Mode 1 is primarily Oldowan "choppers," tools made from pebbles in the Olduvai Gorge area by, mostly, Homo habilis.

Mode 2 includes the Acheulean handaxes found mostly in the Turkana Basin of Kenya, which were made primarily by Homo erectus.

Kariandusi, due to its location in eastern Africa and the age of the site, was likely occupied by Homo erectus who produced Mode 2 technologies.

However, recent climate research has revealed that nearby Lake Elmenteita once reached further inland, and has receded in the past one million years, with the collection at Kariandusi having accumulated due to the water rushing over the land and depositing the hand axes there.

A study by evolutionary biologist Steven Mithen puts out the theory that there was no edge wear because the handaxes weren't used as axes, but as "sexual lures," ways the nearby males would attract females.

Phillipson's team focused on 54 handaxes that appeared to have been used the least, with the least amount of wear on the edges, and analyzed the hand-hold spots on each specimen.