At both Lanet and Engaruka investigations have been carried out before. Already in the late 1930’s Mary Leakey excavated in Hyrax Hill, which is a site not far from Lanet and dated to the then still poorly known Iron Age. In later investigations, notably those by John Sutton of the British Institute in Eastern Africa, one particular section of the site was assigned to the Sirikwa, a pastoral people of the Southern Nilotic linguistic cluster, that occupied the area from Mt.Elgon in the north to the northern Tanzanian steppes in the south between ca. 1400 and 1700. Such depressions were called Sirikwa holes by the local people, and extensive surveys showed that these hollows (which were found to be hut foundations partly dug below the earth surface) were a characteristic feature in the western highlands of Kenya and in northern Tanzania.

A large occurrence of “Sirikwa holes” is situated in Lanet, only four kilometres south-east of Hyrax Hill. Lanet is a partly destroyed site, but at least 60 hollows are still preserved on a gently sloping terrain. From the site opens a magnificent view over the lake of Nakuru and the adjacent Rift Valley basin. A preliminary survey section of Hyrax Hill and a small excavation were made at the site by Merrick Posnansky in 1957. The pottery found represented the same rouletted type as that found already in Hyrax Hill.

Engaruka has been known since 1883 and investigated by the German geologist Hans Reck in 1913. Louis Leakey visited the site in 1935 and made some test excavations in three cairns. More detailed investigations were made there only later, by Hamo Sassoon in 1964 and 1966 and by Peter Robertshaw in 1982; in 1971-72 John Sutton conducted a thorough survey of the archaeological features. The site – that dates according to several radiocarbon analyses between the 15th and 18th centuries - is an extensive system of cultivation installations on the lower talus slopes of the eastern Rift escarpment and on the gently sloping valley bottom to the east. One perennial and a few seasonal rivers descent from the so-called Crater Highlands above the escarpment feeding water into the plateau below; this water has been utilised by the Engaruka community by constructing irrigation channels along which water was distributed into a vast system of cultivation terraces and plots. Also water reservoirs and smaller stoned furrows have been constructed to collect and distribute water even during the dry seasons. The ancient community at Engaruka lived in several villages on the terraced talus slopes. The pottery found in the excavations belongs to a so-far undetermined type, but it seems reasonable to assign the site to the Sonjo, a people belonging to the Bantu linguistic family.

There is still a small re-settled population living in Engaruka and cultivating the fields in the lowermost periphery of the ancient system, and a population of pastoral Maasai herds its cattle on the plains of Engaruka.

Thus, we already know a great deal about Lanet and Engaruka, and especially the latter site has been well surveyed and the information thoroughly analysed especially by John Sutton. But regarding the internal structure and chronological disposition of the sites and especially the size of the original populations that occupied the sites remain still open questions. Our intention is, together with the teams from the University College of London, the University of Stockholm and the British Institute in Eastern Africa, is to shed light on these issues.