title: The pelvis and femur of Ardipithecus ramidus: the emergence of upright walking.
abstract: The femur and pelvis of Ardipithecus ramidus have characters indicative of both upright bipedal walking and movement in trees. Consequently, bipedality in Ar. ramidus was more primitive than in later Australopithecus. Compared with monkeys and Early Miocene apes such as Proconsul, the ilium in Ar. ramidus is mediolaterally expanded, and its sacroiliac joint is located more posteriorly. These changes are shared with some Middle and Late Miocene apes as well as with African apes and later hominids. However, in contrast to extant apes, bipedality in Ar. ramidus was facilitated by craniocaudal shortening of the ilium and enhanced lordotic recurvature of the lower spine. Given the predominant absence of derived traits in other skeletal regions of Ar. ramidus, including the forelimb, these adaptations were probably acquired shortly after divergence from our last common ancestor with chimpanzees. They therefore bear little or no functional relationship to the highly derived suspension, vertical climbing, knuckle-walking, and facultative bipedality of extant African apes.
authors.affiliation: Department of Anthropology, School of Biomedical Sciences, Kent State University, Kent, OH 44242-0001, USA. olovejoy@aol.com
authors.forename: C Owen
authors.initials: CO
authors.lastname: Lovejoy
authors.forename: Gen
authors.initials: G
authors.lastname: Suwa
authors.forename: Linda
authors.initials: L
authors.lastname: Spurlock
authors.forename: Berhane
authors.initials: B
authors.lastname: Asfaw
authors.forename: Tim D
authors.initials: TD
authors.lastname: White
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005002:Ethiopia; D005269:Femur / Q000033:anatomy & histology*; D005580:Fossils; D015186:Hominidae / Q000033:anatomy & histology* / Q000502:physiology*; D007085:Ilium / Q000033:anatomy & histology; D007512:Ischium / Q000033:anatomy & histology; D008124:Locomotion; D010384:Pelvic Bones / Q000033:anatomy & histology*; D010388:Pelvis / Q000033:anatomy & histology; D011187:Posture; D011630:Pubic Bone / Q000033:anatomy & histology; D012272:Ribs / Q000033:anatomy & histology; D013131:Spine / Q000033:anatomy & histology; D013909:Thorax / Q000033:anatomy & histology; D016138:Walking