Abstract and Keywords
This article reviews the fossil evidence for human evolution from the earliest hominins to the emergence of Homo erectus. There are many differences between the hard-tissues of living modern humans and chimps/bonobos. Most researchers agree that the last common ancestor (LCA) of the hominin and panin clades was probably more likely to have been chimp/bonobo-like than modern human-like. The earliest members of the hominin clade would most likely have had smaller canine teeth, larger chewing teeth, and thicker lower jaws as compared to the earliest panins. There would also have been some changes in the skull and postcranial skeleton linked with more time spent upright and with a greater dependence on the hind limbs for bipedal walking. These changes would include a forward shift in the foramen magnum, wider hips, habitually more extended knees, and a narrower, more stable, foot. The group, possible hominins, includes Ardipithecus ramidus, Orrorin tugenensis, Sahelanthropus tchadensis, and Ardipithecus kadabba. The main differences between Ar. Kadabba and Ar. ramidus s. s. (sensu stricto) are that the upper canine crowns of the former have longer crests, and that the P3 crown outline of Ar. kadabba is more asymmetrical, and thus more ape-like, than that of Ar. Ramidus. Another group, archaic hominins, covers two genera, Australopithecus and Kenyanthropus. Australopithecus afarensis is the earliest hominin to have a comprehensive fossil record including a skull, several crania, many lower jaws, and sufficient limb bones to be able to estimate stature and body mass.
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