This specific assertion was made by anthropologist Sherwood Washburn, writing in Scientific American, just as the first reports of a tool-using hominid (Homo habilis) in East Africa were circulating. At the time of her discovery there had already been a few tentative suggestions that the modern human brain might have evolved as a consequence of the increase in tool use among She was the first anatomically bipedal human ancestor to be discovered,Īnd she had an un-apelike hand and a chimpanzee-size brain. Twenty years of careful research on her species have solidified her claim to primacy. Sensation not only in the anthropological world but with the public at large. The best known is Lucy, who lived some 3.2 million years ago in Hadar (in eastern Africa) and whose discovery created an enormous THE EARLIEST DIRECT HUMAN ANCESTORS were the australopithecines, "southern apes" of Africa who walked upright. ODD ARRANGEMENTS AND FUNNY SOLUTIONS ARE THE PROOF OF EVOLUTION-PATHS THAT A SENSIBLE GOD WOULD NEVER TREAD BUT THAT A NATURAL PROCESS, CONSTRAINED BY HISTORY, FOLLOWS PERFORCE. BUT IDEAL DESIGN IS A LOUSY ARGUMENT FOR EVOLUTION, FOR IT MIMICS THE POSTULATEDĪCTION OF AN OMNIPOTENT CREATOR. OUR TEXTBOOKS LIKE TO ILLUSTRATE EVOLUTION WITH EXAMPLES OF OPTIMAL DESIGN-NEARLY PERFECT MIMICRY OF A DEAD LEAF BY A BUTTERFLY OR OF A POISONOUS SPECIES BY A PALATABLE RELATIVE. All rights reserved.How Its Use Shapes the Brain, Language, and Human Culture We do however find some evidence that shoulder configuration allows greater scapular elevation in chimpanzees during arboreal behaviors (e.g., vertical climbing).Ĭhimpanzee Electromyography Kinematic Kinetic Locomotion Vertical climbing.Ĭopyright © 2018 Elsevier Ltd. Our data suggest there is little to no evidence supporting recent hypotheses that the African ape upper thorax and shoulder configuration is an adaptation for knuckle-walking, or more broadly, that knuckle-walking exists as an adaptation to absorb impact shock during terrestriality. Electromyographic results show that activity of the triceps brachii may facilitate energy absorption while serratus anterior likely functions to support the trunk, as in other primates. Ground reaction forces indicate that only a minority of strides in either chimpanzees or macaques have transient forces and, when present, these transient forces as well as loading rates are small. We found that the acromion is significantly more elevated in vertical climbing than during knuckle-walking, while dorsoventral ranges and magnitudes of motion were similar between gaits. We also investigated patterns of recruitment of select forelimb musculature (triceps brachii and serratus anterior) using previously collected data in chimpanzees to determine whether these muscles may function to absorb impact transient forces. We collected 3D kinematic data to quantify motion of the acromion and trunk during quadrupedalism and vertical climbing in chimpanzees as well as ground reaction forces to investigate the presence and magnitude of impact transient forces during terrestrial locomotion in chimpanzees and macaques. Here we test several tenets of these hypotheses using kinematic and kinetic data from chimpanzees and macaques, and electromyographic data of shoulder muscle activity in chimpanzees. Recently it has been proposed that these traits are instead adaptations for knuckle-walking, and more broadly, that knuckle-walking itself is an adaptation for shock absorption during terrestriality. Great apes exhibit a suite of morphological traits of the shoulder and upper thorax that have traditionally been linked to orthograde arborealism.
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