The distal end of a hominoid humerus was recovered from early Pleistocene sediments in the Kanapoi drainage near the southern end of Lake Rudolf. Lava capping the sediments yielded a potassium/argon date of 2.5 million years. The fragment can be distinguished on inspection from gorilla and orangutan; discriminate analysis of humeri of Homo and Pan assigns it as hominid. From other evidence we consider it more likely to represent Australopithecus s.s. than Paranthropus.