抄録
The ∼4.5 Ma Ardipithecus ramidus is represented by well over 100 specimens from more than 30 to 60 individuals recovered from the Middle Awash and Gona research areas, Ethiopia. These fossils include a partial skeleton of Ar. ramidus from Aramis, as well as other informative postcranial and dentognathic remains, such as over 20 canines almost certainly from different individuals. Recent analyses of the Ar. ramidus fossils, published in October 2009, indicate that Ar. ramidus was phylogenetically ancestral to, or the immediate outgroup of, the Australopithecus anamensis/afarensis lineage, and combined substantial arboreal capabilities with an Australopithecus-like upper pelvic balance mechanism for bipedal locomotion. The generalized forelimb and foot morphologies of Ar. ramidus suggest that it did not share a suspensory, advanced vertical climbing, and/or knuckle walking heritage with modern African apes. The Ar. ramidus dentition indicates loss of functional male canine honing by 6 to 4.4 Ma. Its incisal/postcanine morphology, wear and enamel isotopics suggest a predominantly woodland-based frugivorous/omnivorous diet, lacking specializations seen in Gorilla, Pan or Australopithecus. The Ar. ramidus cranium shares with that of Sahelanthropus a short basicranium and a lack of morphologies associated with heavy chewing. The Ar. ramidus skull was absolutely and relatively small, in keeping with its reduced male canine size, and inferred weak sexual dimorphism in cranial and body size. Comparisons suggest enhanced canine size and facial prognathism in Pan troglodytes, a general facial and dental size reduction in Pan paniscus, and exaggerated sexual dimorphism and allometric and/or dietary effects in the Gorilla cranium. Considerable specializations involving dietary, locomotor, and social behaviors are inferred in each of the modern African ape species. Both the Ar. ramidus and Miocene ape evidence supports the hypothesis of extensive parallel evolution of modern-ape like suspensory adaptations, suggesting a Pongo-African ape divergence deep in the early Miocene. This in turn conforms to Pan and Gorilla divergences of ∼8 and ∼11 Ma, respectively, from the human lineage.
