The Namoratunga sites contain a large quantity of engraved rock art, including geometric designs linked to branding symbols used by modern east African pastoralists.
The Maasai people, though now living further south, are recorded to have lived near Lokori in the northern Kerio river valley as recently as 1400 A.D. Ceramic cultures associated with Nilotic people like the Maasai or Turkana may have first moved into the region between 450-1100 A.D., if not earlier.