Glynn Isaac and Richard Leakey's 'Sonjo Expedition' in 1963-64 (to examine Pleistocene fossiliferous strata) discovered Sonjo living and cultivating at Peninyi.
A field study conducted by Glynn Isaac and Richard Leakey in 1963-64 focused on examining the Pleistocene-era rock layers, which showed that the Sonjo people were living and working the land at Peninyi.