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Science 2 October 2009:
Vol. 326. no. 5949, pp. 73, 100-106
DOI: 10.1126/science.1175833
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Research Articles

The Great Divides: Ardipithecus ramidus Reveals the Postcrania of Our Last Common Ancestors with African Apes

C. Owen Lovejoy,1,* Gen Suwa,2,* Scott W. Simpson,3 Jay H. Matternes,4 Tim D. White5

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.

1 Department of Anthropology, School of Biomedical Sciences, Kent State University, Kent, OH 44242–0001, USA.
2 The University Museum, the University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
3 Department of Anatomy, Case Western Reserve University School of Medicine, Cleveland, OH 44106–4930, USA.
4 4328 Ashford Lane, Fairfax, VA 22032, USA.
5 Human Evolution Research Center, and Department of Integrative Biology, 3101 Valley Life Sciences, University of California at Berkeley, Berkeley, CA 94720, USA.

* To whom correspondence should be addressed. E-mail: olovejoy{at}aol.com (C.O.L.); suwa{at}um.u-tokyo.ac.jp (G.S.)

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Ardipithecus ramidus and the Paleobiology of Early Hominids.
T. D. White, B. Asfaw, Y. Beyene, Y. Haile-Selassie, C. O. Lovejoy, G. Suwa, and G. WoldeGabriel (2009)
Science 326, 64-64, 75-86
   Abstract »    Full Text »    PDF »
The Ardipithecus ramidus Skull and Its Implications for Hominid Origins.
G. Suwa, B. Asfaw, R. T. Kono, D. Kubo, C. O. Lovejoy, and T. D. White (2009)
Science 326, 68-68, 68e1-68e7
   Abstract »    Full Text »    PDF »
Careful Climbing in the Miocene: The Forelimbs of Ardipithecus ramidus and Humans Are Primitive.
C. O. Lovejoy, S. W. Simpson, T. D. White, B. Asfaw, and G. Suwa (2009)
Science 326, 70-70, 70e1-70e8
   Abstract »    Full Text »    PDF »
The Pelvis and Femur of Ardipithecus ramidus: The Emergence of Upright Walking.
C. O. Lovejoy, G. Suwa, L. Spurlock, B. Asfaw, and T. D. White (2009)
Science 326, 71-71, 71e1-71e6
   Abstract »    Full Text »    PDF »
Reexamining Human Origins in Light of Ardipithecus ramidus.
C. O. Lovejoy (2009)
Science 326, 74-74, 74e1-74e8
   Abstract »    Full Text »    PDF »


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