The first fossilized specimen of the species , though not recognized as such at the time , was a single arm bone found in Pliocene strata in the Kanapoi region of East Lake Turkana by a Harvard University research team in 1965 . The first fossilized specimen of the species , though not recognized as such at the time , was a single fragment of humerus ( arm bone ) found in Pliocene strata in the Kanapoi region of East Lake Turkana by a Harvard University research team in 1965 .