Lake Turkana is the largest permanent desert lake on Earth, 250 kilometres of jade-green water in the lava badlands of northern Kenya, in Turkana county on the Ethiopian border, with volcanic islands full of crocodiles rising from it, and its shores hold the richest record of human origins found anywhere. The lake has no outlet and lies in the Rift Valley among black lava fields and wind, fed by the Omo river from Ethiopia, and the algae that give it the name Jade Sea turn the water a green that changes with the light; it is a hard place to reach, a long drive on rough roads from Marsabit or Kitale to the fishing villages of Loiyangalani on the east shore or Kalokol on the west, where rows of wooden and fibreglass boats line the beaches and the crews mend nets in whatever shade there is until the fierce afternoon wind falls away. Central Island, ringed by three crater lakes inside its rim, is one of the great breeding grounds of the Nile crocodile, called Crocodile Island by the locals, and it and South Island, both active volcanic cones, are landed on by boat with a ranger.
The eastern shore is Koobi Fora and the Sibiloi national park, where the eroding badlands have given up more early-human fossils than almost anywhere, with skulls of Homo habilis, Homo erectus and the robust australopithecines found by Richard Leakey's teams from the 1960s, and on the western shore in 1984 the fossil hunter Kamoya Kimeu spotted a scrap of skull on a dry riverbed at Nariokotome, the first trace of the most complete Homo erectus skeleton ever found, the Turkana Boy. Around the lake live the Turkana, Rendille and Samburu herders and, on the southeastern shore, the El Molo, a fishing people counted among the smallest ethnic groups in Kenya. The Loiyangalani festival each year brings the peoples of the lake together, and dams on the Omo in Ethiopia threaten its water. Lake Turkana is a sea in the desert where humans began, and the crocodiles have it now.