The great divides: Ardipithecus ramidus reveals the postcrania of our last common ancestors with African apes.

Bibliographic Collection: 
MOCA Reference, APE
Publication Type: Journal Article
Authors: Lovejoy, C Owen; Suwa, Gen; Simpson, Scott W; Matternes, Jay H; White, Tim D
Year of Publication: 2009
Journal: Science
Volume: 326
Issue: 5949
Pagination: 100-6
Date Published: 2009 Oct 2
Publication Language: eng
ISSN: 1095-9203
Keywords: Animals, Biological Evolution, Body Size, Body Weight, Bone and Bones, Ethiopia, Extremities, Foot Bones, Fossils, Gorilla gorilla, Hand Bones, Hominidae, Humans, Locomotion, Metacarpal Bones, Pan troglodytes, Pelvic Bones, Posture, Skeleton, Spine, Trees, Walking

Genomic comparisons have established the chimpanzee and bonobo as our closest living relatives. However, the intricacies of gene regulation and expression caution against the use of these extant apes in deducing the anatomical structure of the last common ancestor that we shared with them. Evidence for this structure must therefore be sought from the fossil record. Until now, that record has provided few relevant data because available fossils were too recent or too incomplete. Evidence from Ardipithecus ramidus now suggests that the last common ancestor lacked the hand, foot, pelvic, vertebral, and limb structures and proportions specialized for suspension, vertical climbing, and knuckle-walking among extant African apes. If this hypothesis is correct, each extant African ape genus must have independently acquired these specializations from more generalized ancestors who still practiced careful arboreal climbing and bridging. African apes and hominids acquired advanced orthogrady in parallel. Hominoid spinal invagination is an embryogenetic mechanism that reoriented the shoulder girdle more laterally. It was unaccompanied by substantial lumbar spine abbreviation, an adaptation restricted to vertical climbing and/or suspension. The specialized locomotor anatomies and behaviors of chimpanzees and gorillas therefore constitute poor models for the origin and evolution of human bipedality.

Alternate Journal: Science
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