ape language latest issue journal nih research vol 7 1 jan 1995 pp 5055 contains short review article pat shipman human evolution cover article referred fading lines apes humans actually titled climbing family tree makes hominid hominid discussion linguistic abilities might interest subscribers linguist list author discusses kanzi sue savage rumbaugh 1994 book kanzi ape brink human mind john wiley sons ny according savage rumbaugh kanzi rudimentary grammar use displaced referents arbitrary symbols case icons lexigrams computer r thinks ability equals 2 year old child later section work derek bickerton language species 1990 university chicago press summarized bickerton admits kanzi apes young children use protolanguage full language lack grammatical elements rest section language devoted broca area cortical specialization john