The first fossils were discovered in 1972 along Lake Turkana (at the time called Lake Rudolf) in Kenya, and were detailed by Kenyan palaeoanthropologist Richard Leakey the following year. The specimens were: a large and nearly complete skull (KNM-ER 1470, the lectotype) discovered by Bernard Ngeneo, a local; a right femur (KNM-ER 1472) discovered by Dr. J. Harris; an upper femur (proximal) fragment (KNM-ER 1475) discovered by fossil collector Kamoya Kimeu; and a complete left femur (KNM-ER 1481) discovered by Harris. However, it is unclear if the femora belong to the same species as the skull. He classified them under the genus "Homo" because he had reconstructed the skull fragments so that it had a large brain volume and a flat face, but did not assign them to a species. Because the horizon they were discovered in was, at the time, dated to 2.9–2.6 million years ago (mya), Leakey thought these specimens were a very early human ancestor. This challenged the major model of human evolution at the time where "Australopithecus africanus" gave rise to "Homo" about 2.5 mya, but if "Homo" had already existed at this time, it would call for serious revisions. However, the area was redated to about 2 mya in 1977 (the same time period as "H. habilis" and "H. ergaster"/"H. erectus"), and more precisely to 2.1–1.95 mya in 2012. They were first assigned to the species "habilis" in 1975 by anthropologists Colin Groves and Vratislav Mazák. In 1978, in a joint paper with Leakey and English anthropologist Alan Walker, Walker suggested the remains belong in "Australopithecus" (and that the skull was incorrectly reconstructed), but Leakey still believed they belonged to "Homo", though they both agreed that the remains could belong to "habilis".