In 1963 Richard Leakey discovered the Pleistocene deposits at Lake Natron while flying in a small plane from Nairobi to Olduvai Gorge. In this same year Leakey, along with Glynn Isaac, undertook a brief exploration in the area. In January 1964, Leakey and Isaac set out for Lake Natron on the first archaeological survey in the region. On the 11th of January an exceptional find was made that would place Peninj on the maps of Palaeoanthropology: a remarkable jawbone of the species Paranthropus boisei. The publication of the finding in April of 1964 was the ticket for Isaac and Leakey to embark on a second expedition between July and September. Their expedition undertook a comprehensive geological study of the Natron Basin and provided a description of a sedimentary sequence that Isaac gave the name of Peninj Group. Two important Early Acheulean sites were also recorded and excavated at the top of the Sambu Escarpment, which were then given the names MHS and RHS.


After his splendid research project at Koobi Fora (Kenya), Isaac took renewed interest in Peninj in 1981. A new project started up in 1982, with an international team co-led by Isaac, the Tanzanian Amini Mturi, and the Frenchman Maurice Taieb. Unfortunately, only superficial archaeological studies could be undertaken, and the sudden death of Isaac in 1985 was a dramatic blow to their starting in earnest.

In 1994, Manuel Dominguez-Rodrigo (Complutense University of Madrid) led the first Spanish palaeoanthropological expedition to Peninj, accompanied by the geologists and paleontologists Luis de Luque and Luis Alcal√°, among others. Until 2005, continuous fieldwork and extensive excavations were undertaken, and spatial, technological, taphonomic and functional studies were performed.

A Spanish archaeological presence has continued in the area since 2007, with a new team, led by Fernando Diez Martin (University of Valladolid), working on enlarging previous research at Peninj and particularly focused on the Acheulean sites located on the Escarpments.