Independent evolution of knuckle-walking in African apes shows that humans did not evolve from a knuckle-walking ancestor
25 Aug 2009-Proceedings of the National Academy of Sciences of the United States of America (National Academy of Sciences)-Vol. 106, Iss: 34, pp 14241-14246
TL;DR: The presence of purported knuckle-walking features in the hominin wrist can be viewed as evidence of arboreality, not terrestriality, and provide evidence that human bipedalism evolved from a more arboreal ancestor occupying the ecological niche common to all living apes.
Abstract: Despite decades of debate, it remains unclear whether human bipedalism evolved from a terrestrial knuckle-walking ancestor or from a more generalized, arboreal ape ancestor. Proponents of the knuckle-walking hypothesis focused on the wrist and hand to find morphological evidence of this behavior in the human fossil record. These studies, however, have not examined variation or development of purported knuckle-walking features in apes or other primates, data that are critical to resolution of this long-standing debate. Here we present novel data on the frequency and development of putative knuckle-walking features of the wrist in apes and monkeys. We use these data to test the hypothesis that all knuckle-walking apes share similar anatomical features and that these features can be used to reliably infer locomotor behavior in our extinct ancestors. Contrary to previous expectations, features long-assumed to indicate knuckle-walking behavior are not found in all African apes, show different developmental patterns across species, and are found in nonknuckle-walking primates as well. However, variation among African ape wrist morphology can be clearly explained if we accept the likely independent evolution of 2 fundamentally different biomechanical modes of knuckle-walking: an extended wrist posture in an arboreal environment (Pan) versus a neutral, columnar hand posture in a terrestrial environment (Gorilla). The presence of purported knuckle-walking features in the hominin wrist can thus be viewed as evidence of arboreality, not terrestriality, and provide evidence that human bipedalism evolved from a more arboreal ancestor occupying the ecological niche common to all living apes.
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01 Jan 2016
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TL;DR: The Ardipithecus ramidus hand and wrist exhibit none of the derived mechanisms that restrict motion in extant great apes and are reminiscent of those of Miocene apes, such as Proconsul.
Abstract: The Ardipithecus ramidus hand and wrist exhibit none of the derived mechanisms that restrict motion in extant great apes and are reminiscent of those of Miocene apes, such as Proconsul. The capitate head is more palmar than in all other known hominoids, permitting extreme midcarpal dorsiflexion. Ar. ramidus and all later hominids lack the carpometacarpal articular and ligamentous specializations of extant apes. Manual proportions are unlike those of any extant ape. Metacarpals 2 through 5 are relatively short, lacking any morphological traits associable with knuckle-walking. Humeral and ulnar characters are primitive and like those of later hominids. The Ar. ramidus forelimb complex implies palmigrady during bridging and careful climbing and exhibits none of the adaptations to vertical climbing, forelimb suspension, and knuckle-walking that are seen in extant African apes.
230 citations
TL;DR: It is shown that humans seem to mimic external support by creating a virtual pivot point (VPP) above their centre of mass, and a highly reduced conceptual walking model reveals that such virtual support is sufficient for achieving and maintaining postural stability.
Abstract: Habitual bipedalism is considered as a major breakthrough in human evolution and is the defining feature of hominins. Upright posture is presumably less stable than quadrupedal posture, but when using external support, for example, toddlers assisted by their parents, postural stability becomes less critical. In this study, we show that humans seem to mimic such external support by creating a virtual pivot point (VPP) above their centre of mass. A highly reduced conceptual walking model based on this assumption reveals that such virtual support is sufficient for achieving and maintaining postural stability. The VPP is experimentally observed in walking humans and dogs and in running chickens, suggesting that it might be a convenient emergent behaviour of gait mechanics and not an intentional locomotion behaviour. Hence, it is likely that even the first hominis may have already applied the VPP, a mechanism that would have facilitated the development of habitual bipedalism.
184 citations
TL;DR: High levels of hand disparity among modern hominoids are revealed, which are explained by different evolutionary processes: autapomorphic evolution in hylobatids (extreme digital and thumb elongation), convergent adaptation between chimpanzees and orangutans (digital elongation) and comparatively little change in gorillas and hominins.
Abstract: Human hands are distinguished from apes by possessing longer thumbs relative to fingers. However, this simple ape-human dichotomy fails to provide an adequate framework for testing competing hypotheses of human evolution and for reconstructing the morphology of the last common ancestor (LCA) of humans and chimpanzees. We inspect human and ape hand-length proportions using phylogenetically informed morphometric analyses and test alternative models of evolution along the anthropoid tree of life, including fossils like the plesiomorphic ape Proconsul heseloni and the hominins Ardipithecus ramidus and Australopithecus sediba. Our results reveal high levels of hand disparity among modern hominoids, which are explained by different evolutionary processes: autapomorphic evolution in hylobatids (extreme digital and thumb elongation), convergent adaptation between chimpanzees and orangutans (digital elongation) and comparatively little change in gorillas and hominins. The human (and australopith) high thumb-to-digits ratio required little change since the LCA, and was acquired convergently with other highly dexterous anthropoids.
149 citations
TL;DR: A new equation that mathematically corrects the quadrupedal equations for use in bipeds is presented, derived from the systemic difference in the circumference-to-area scaling relationship of two circles (hypothetical quadruped) and one circle (Hypothetical biped), which represent the cross-section of the main weight-bearing limb bones.
Abstract: Summary 1. Body mass is strongly related to both physiological and ecological properties of living organisms. As a result, generating robust, broadly applicable models for estimating body mass in the fossil record provides the opportunity to reconstruct palaeobiology and investigate evolutionary ecology on a large temporal scale. 2. A recent study provided strong evidence that the minimum circumference of stylopodial elements (humerus and femur) is conservatively associated with body mass in living quadrupeds. Unfortunately, this model is not directly applicable to extinct bipeds, such as non-avian dinosaurs. 3. This study presents a new equation that mathematically corrects the quadruped equ ation for use in bipeds. It is derived from the systemic difference in the circumference-to-area scaling relationship of two circles (hypothetical quadruped) and one circle (hypothetical biped), which represent the cross-section of the main weight-bearing limb bones. 4. When applied to a newly constructed data set of femoral circumferences and body masses in living birds, the new equation reveals errors that are significantly lower than other published equations, but significantly higher than the error inherent in the avian data set. Such errors, however, are expected given the unique overall femoral circumference–body mass scaling relationship found in birds. 5. Body mass estimates for a sample of bipedal dinosaurs using the new model are consistent with recent estimates based on volumetric life reconstructions, but, in contrast, this equation is simpler to use, with the concomitant potential to provide a wider set of body mass estimates for extinct bipeds. 6. Although it is evident that no one estimation model is flawless, the combined use of the corrected quadrupedal equations and the previously published quadrupedal equation offer a consistent approach with which to estimate body masses in both quadrupeds and bipeds. These models have implications for conducting large-scale macroevolutionary analyses of body size throughout the evolutionary history of terrestrial vertebrates, and, in particular, across major changes in body plan, such as the evolution of bipedality in archosaurs and quadrupedality in
117 citations
Cites background from "Independent evolution of knuckle-wa..."
...…to bipedal dinosaurs, but rather offers the possibility to investigate the evolution of body size across all postural transitions in terrestrial tetrapod evolution (Spoor, Wood & Zonneveld 1994; Steudel 1996; Berman et al. 2000; Nesbitt & Norell 2006; Kivell & Schmitt 2009;Maidment&Barrett 2012)....
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References
More filters
Book•
15 Jun 1996
TL;DR: In "The Shape of Life", Raff analyzes the rise of this experimental discipline and lays out research questions, hypotheses and approaches to guide its development.
Abstract: In the book, "Embryos, Genes, and Evolution", Raff and co-author Thomas Kaufman proposed a synthesis of developmental and evolutionary biology. In "The Shape of Life", Raff analyzes the rise of this experimental discipline and lays out research questions, hypotheses and approaches to guide its development. Raff uses the evolution of animal body plans to exemplify the interplay between developmental mechanisms and evolutionary patterns. Animal body plans emerged half a billion years ago. Evolution within these body plans during this span of time has resulted in the tremendous diversity of living animal forms. Raff argues for an integrated approach to the study of the intertwined roles of development and evolution involving phylogenetic, comparative and functional biology. This synthesis should interest not only scientists working in these areas, but also paleontologists, zoologists, morphologists, molecular biologists and geneticists.
1,167 citations
"Independent evolution of knuckle-wa..." refers background in this paper
...analyses can provide a critical insight into the homology and function of morphological features that cannot be gained from adult morphology alone (25, 26)....
[...]
TL;DR: Experimental and comparative evidence suggests that cortical bone is primarily responsive to strain prior to sexual maturity, both in terms of the rate of new bone growth (modeling) as well as rates of turnover (Haversian remodeling).
Abstract: The premise that bones grow and remodel throughout life to adapt to their mechanical environment is often called Wolff's law. Wolff's law, however, is not always true, and in fact comprises a variety of different processes that are best considered separately. Here we review the molecular and physiological mechanisms by which bone senses, transduces, and responds to mechanical loads, and the effects of aging processes on the relationship (if any) between cortical bone form and mechanical function. Experimental and comparative evidence suggests that cortical bone is primarily responsive to strain prior to sexual maturity, both in terms of the rate of new bone growth (modeling) as well as rates of turnover (Haversian remodeling). Rates of modeling and Haversian remodeling, however, vary greatly at different skeletal sites. In addition, there is no simple relationship between the orientation of loads in long bone diaphyses and their cross-sectional geometry. In combination, these data caution against assuming without testing adaptationist views about form-function relationships in order to infer adult activity patterns from skeletal features such as cross-sectional geometry, cortical bones density, and musculo-skeletal stress markers. Efforts to infer function from shape in the human skeleton should be based on biomechanical and developmental models that are experimentally tested and validated.
683 citations
Book•
01 Jan 1995
TL;DR: In this article, the relationship between climatic and biotic evolution is addressed, focusing on how climatic change during the last 15 million years - especially the last three million - has affected human evolution and other evolutionary events.
Abstract: Addressing the relationship between climatic and biotic evolution, this work focuses on how climatic change during the last 15 million years - especially the last three million - has affected human evolution and other evolutionary events.
627 citations
Book•
[...]
01 Jul 1996
TL;DR: This book discusses chimpanzees, Savanna chimpanzees, referential models and the Last Common Ancestor, and a new milestone in great ape research Junichiro Itani's research.
Abstract: Preface Foreword: conserving Great Apes Jane Goodall Part I. Apes Overviewed: 1. Towards an understanding of the orangutan's social system Carel van Schaik and Jan van Hooff 2. Comparative socio-ecology of gorillas David Watts 3. Comparative socio-ecology of Pan paniscus Frances J. White Part II. Social Ecology: 4. Social ecology of Kanyawara chimpanzees Richard Wrangham 5. Ranging and social structure of lowland gorillas in the Lope Reserve, Gabon Caroline Tutin 6. Sympatric chimpanzees and gorillas in the Ndoki Forest, Congo Suehisa Kuroda, Tomoaki Nishihara, Shigeru Suzuki and Rufin A. Oko 7. Dietary and ranin overlap in sympatric gorillas and chimpanzees in Kahuzi-Biega National Park, Zaire Juichi Yamagiwa, Tamaki Maruhashi, Takakazu Yumoto and Ndunda Nwanza Part III. Social Relations: 8. Social grouping in Tai chimpanzees 9. Coalition strategies among adult male chimpanzees of the Mahale Mountains, Tanzania Toshisada Nishida and Kazuhiko Hosaka 10. Male rank order and copulation rate in a unit-group of bonobos at Wamba, Zaire Takayoshi Kano 11. Comparing copulations of chimpanzees and bonobos Yukio Takahata, Hiroshi Ihobe and Gen'ichi Idani Part IV. Minds: 12. Conflict as negotiation Frans de Waal 13. Language perceived: Paniscus branches out E. S. Savage-Rumbaugh, S.Williams, T. Furuichi and T. Kano 14. Reciprocation in apes C. K. Hemelrijk 15. Chimpanzee intelligence in nature and captivity Tetsuro Matsuzawa Part V. Apes Compared: 16. Comparative positional behavior of the African apes Diane Doran 17. Nest-building behavior in the great apes Barbara Fruth and Gottfried Hohmann 18. Comparative studies of African ape vocal behavior John Mitani 19. On which side of the apes? Ethological study of laterality of hand use W. C. McGrew and L. F. Marchant Part VI. Modelling Ourselves: 20. Savanna chimpanzees, referential models and the Last Common Ancestor Jim Moore 21. Reconstructions reconsidered: Chimpanzee models and human evolution Adrienne Zihlman Afterword - A new milestone in great ape research Junichiro Itani Appendix: Study sites Index.
535 citations