Whilst the European explorers were setting their feet to epic deeds wishing to be the first to unveil the sources of the Nile, the inland of Kenya remained hidden for the West. With the exception of Rebmann's and Krapf's incursions, fear of the Maasai warriors and of the hard climatic conditions in the Taru desert, which extended beyond the shoreline, kept unknown for years the shortest way to reach the birthplace of the great river, north of Lake Victoria. The history of inner Kenya during the whole previous period is a story of migrations, invasions and wars between rival tribes that had never met the white man. It would be Thomson who would finally link these people's destiny to that of the foreigners who were disputing the control of the coast.

The map of inner Kenya was mainly populated by Bantus, Cushites and Nilotes during the first centuries of our era. As opposed to the kingdoms of Buganda, which possessed a complex and defined territorial structure reflected in solid and stable settlings, the Kenyan tribes constituted peoples without States. Frequent invasions and bloody fights have erased almost completely the historical footprints of those moves. The Sirikwa, of Bantu origin, even built solid stone constructions in the 17th and 18th centuries, but they were exterminated by Camitic and Nilotic tribes.

Migrations and invasions were motivated by the search of new pastures and more fertile lands, as well as by the wish to seize the wealth of the neighbouring tribes, their cattle and their women. The attacked tribes fled to quieter territories, subsequently obliging other settlers to move farther beyond. Over the centuries, the different tribes established commercial relationships and alliances to cope with the drought periods.

Until the 16th century, several ethnic groups inhabited the Bantu areas from Eastern Uganda to Lake Victoria. The south of the lake and the Nyanza province were populated by the Kisii. From the year 1500, the Luos started to invade the northeastern flank of the lake. Some resident tribes were integrated by the new settlers, but others were pushed northwards and eastwards, taking the Buluyia land and grouping together in what we now know as the Luyha people. The Kisii, pressed by the Luos and by the wars of Maasais and Kipsigis, migrated northwards to their current lands in Kisii Hills.

In Eastern Kenya, the entry of the Somalis, northern Cushites coming from the Horn of Africa and possibly natives of Arabia, displaced the Boran and Galla people, also Cushites. Borans moved to the region of Wajir, while the Gallas' migration eastward pushed the Eastern Bantu groups, located at the north coast, southwards and westwards. The Mijikendas settled south of Malindi, whilst Kikuyus and Embus moved inland following the Tana river.

Coming from the region north of Lake Turkana, the Nilotic Maasai people moved southward, assimilating along the way some of the Kalenjin groups. In the early 18th century, the Maasais dominated the central Kenyan lands farther to the north of what today is Tanzania. Their warrior spirit prevented the Arab slave traders from exploiting the northern routes, and their persistent attacks to the neighbouring tribes searching for cattle and pastures obliged the latter to migrate. Fleeing from the Maasais, the Kikuyu people found a shelter in the Highlands' forest areas. Later on, from 1840 to 1870, the Maasais engaged themselves in a series of internal fights between rival clans that brought decadence to this tribe. During this decline, some Maasai clans mixed up with their neighbours Kikuyus, Tavetas and Chagas in Tanzania. Even today, the Maasais believe that the day will come in which they will recover their former splendour.

Along the 19th century, the Kambas started to arrange caravans carrying ivory from the inner lands to the coastal trade centers. Meanwhile, in the western regions, the Nandis took advantage of the Maasais' weakness to become the most powerful group in the area at the end of the century, dominating the Luyhas and Luos, right at the time when the white men were launching their expeditions to the unspoiled lands of inner Kenya.