Asa Issie, Aramis and the origin of

The origin of Australopithecus, the genus widely interpreted as ancestral to Homo, is a central problem in humanevolutionary studies. Australopithecus species differ markedly from extant African apes and candidate ancestral hominidssuch as Ardipithecus, Orrorin and Sahelanthropus. The earliest described Australopithecus species is Au. anamensis, theprobable chronospecies ancestor of Au. afarensis. Here we describe newly discovered fossils from the Middle Awashstudy area that extend the known Au. anamensis range into northeastern Ethiopia. The new fossils are fromchronometrically controlled stratigraphic sequences and date to about 4.1–4.2million years ago. They include diagnosticcraniodental remains, the largest hominid canine yet recovered, and the earliest Australopithecus femur. These newfossils are sampled from a woodland context. Temporal and anatomical intermediacy between Ar. ramidus andAu. afarensis suggest a relatively rapid shift from Ardipithecus to Australopithecus in this region of Africa, involving eitherreplacement or accelerated phyletic evolution.