by C. Owen Lovejoy
Department of Anthropology, Division of Biomedical Sciences, Matthew Ferrini Institute of Human Evolutionary Research, Kent State University, Kent, OH 44242, USA
ABSTRACT
THE HUMAN FOSSIL RECORD IS ONE OF THE MOST COMPLETE FOR ANY MAMMAL. A BASAL ANCESTRAL SPECIES, AUSTRALOPITHECUS AFARENSIS, EXHIBITS A WELL-PRESERVED POSTCRANIUM THAT PERMITS RECONSTRUCTION OF IMPORTANT EVENTS IN THE EVOLUTION OF OUR LOCOMOTOR SKELETON. WHEN COMPARED WITH THOSE OF LIVING APES AND MODERN HUMANS, THIS SPECIES PROVIDES A NUMBER OF INSIGHTS INTO THE ORIGIN AND DESIGN OF THE MODERN HUMAN FRAME AS WELL AS THE SELECTIVE AGENCIES THAT HAVE GUIDED ITS EVOLUTION DURING THE PAST THREE MILLION YEARS. EVOLUTIONARY ASPECTS OF THE HUMAN SPINE AND PELVIS ARE REVIEWED, INCLUDING THEIR IMPACT ON SEVERAL CLINICALLY RELEVANT ASPECTS OF HUMAN GAIT AND POSTURE.
© 2004 ELSEVIER B.V. ALL RIGHTS RESERVED.
I. INTRODUCTION
The human musculoskeletal system has been rigorously examined for centuries, and human gait has been experimentally analyzed with an almost equal intensity [1]. Our knowledge has been amassed largely for its clinical implications, and while an understanding of the mechanics of quiet human walking is critical to endeavors such as implant design and surgical intervention, it provides little information about the manner in which natural selection molded our lower limb during the last several million years. Bipedality is commonly performed by a variety of primates and other mammals, even some artiodactyls. Human ancestors, however, adopted this odd gait as their exclusive form of locomotion, and so extensively modified their postcranium that every transport event, whether a simple stroll of a few yards or a desperate flight to avoid an attacking predator, became restricted to its use. When and why did this transition take place? What has been the sequence of anatomical changes during its fixation? What insights do they provide with respect to common human musculoskeletal disorders? These are questions whose answers can supply important information to the clinician, because the natural history of a structure affords a unique perspective otherwise unavailable using only extant anatomy and performance. Complete answers to these kinds of questions require an examination of our fossil record.
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