The Evolution of Bipedalism in Lucy, the Australopithecus afarensis

Topics: Australopithecus afarensis, Hominina, Bipedalism Pages: 5 (1591 words) Published: November 11, 2013
Introduction
Australopithecus afarensis have commonly been found in sites such as Hadar, Ethiopia and Laetoli, Tanzania. An Australopithecus afarensis fossil was discovered in Hadar, Ethiopia in 1974, by Donald Johanson. This fossil was scientifically known as Afar Locality (AL) 288-1 but would be commonly called Lucy. The significance of this fossil was that it contained 40% of its skeleton thus it became one of the most complete individual to be discovered. When Lucy’s skeletal remains were first discovered, many archaeologists worked hard to put together all forty seven bones, in order to understand the physical structure and to derive many unknown answers related to habitat, skills and diet. But most importantly, her structure explains to many her locomotion which was the big question during that period. The discovery of the footprints in Tanzania have allowed researchers to make specific clear arguments about the locomotion patterns of these early hominins and have concluded that these hominins were bipedal but were not similar to the locomotion pattern of modern humans. According to Lewis et al. (2010), bipedal locomotion is defined as ‘walking habitually on two feet, walking habitually on two legs is the single most distinctive feature of hominins. To this date, there have been many controversies on “to what extent was Lucy bipedal?” which has been supported through evidences such as, the analysis of Lucy’s skeleton particularly her femur, careful examinations of the footprints in Laetoli and surveying the habitat of A.afarensis over a period of time.

Skeleton
Paleoanthropologist Donald Johanson worked at a site near Hadar (Fig1-1), in 1973 where he had discovered a humanlike knee joint that appeared to be 3 million years old. He returned to the United States of America to show his discovery to Own Lovejoy, an anthropologist. Lovejoy was certain that the joint was an adult hominid that walked on two legs and had to be about 3 feet tall. Within the same year, Johanson returned to the site where he found forty seven bones of an early hominid skeleton. Lucy was officially named after a song by the Beatles. She was determined to be an Australopithecus afarensis since she was found within the Afar region of Ethiopia. She was determined to be 3.2 million years B.P from potassium-argon dating. Lucy was believed to be 3 feet and 6 inches tall with characteristics that were both ape-like and human-like. The upper portion of her body was said to be more ape-like because she had arms that were longer than her legs and a system of joints that heavily reflected a semi-arboreal lifestyle. However, the structure of her legs and pelvis showed that she was able to walk on two legs and it was declared to be solid evidence to prove that early hominins were bipedal. (Gardner, 1999) Lucy’s locomotory apparatus was more human like because she had a “wide pelvis, a necked femur, and a double curvature of the spine which all indicated the ability to walk upright.” (Coppens et al., 2004) Lucy was similar to humans because of her femur since she had “closely spaced knees and wide hips with femurs that angled inward and made it possible for her to keep her center of gravity over her feet.” (Gardner, 1999, p. 67) However, A.afarensis had curved hands and this indicated that they were still partly arboreal. The fact that Lucy walked on two legs was widely accepted but what gait she preferred was widely debated. This question was analyzed by a study done by Crompton et al., which showed that a bent-hip and a bent-knee motion is less mechanically effective and that heat generation is much greater and an erect carriage was favored, thus including that Lucy walked tall (Crompton et al., 1998).

Figure 1-1
Map of Hadar, Ethiopia (top right hand corner) site where Lucy was found in 1973 by Donald Johanson. (http://www.achievement.org/autodoc/photocredit/achievers/joh1-026)

Footprints
The 3.6 million years old footprints found in...


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Coppens, Y., Buchet, N. and Dagneaux, P. 2003. Human Origins: The Story of our Species. Singapore: Tien Wah Press
Crompton, R.H., Weijie, L.Y.W., Gunther, M
Duncan, A.S., Kappelman, J. and Shapiro L.J. 2005. Metatarsophalangeal joint function and positional behavior in Australopithecus afarensis. American Journal of Physical Anthropology 93: 67-81
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Johanson, D. – Academy of Achievement Photo Credit, Academy of Achievement Main Menu Web. Accessed November 16, 2012
http://www.achievement.org/autodoc/photocredit/achievers/joh1-026
Jungers, W. L. 1982. Lucy’s limbs: skeletal allometry and locomotion in Australopthecus afarensis. Nature 297: 676 – 678

Lewis, B., Jurmain, R. and Kilgore, L. 2010. Understanding Humans: Introduction to Physical Anthropology and Archaeology. Wadsworth Cengage Learning.
Raichlen, D. A., Gordon, A. D., Harcourt-Smith. W. E. H., Foster, A .D. and Haas Jr, W. R. 2010. Laetoli Footprints Preserve Earliest Direct Evidence of Human-Like Bipedal Biomechanics. PLos One 5: 1-6
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Ward, C. V., Kimbel, W. H. and Johanson, D.C. 2011. Complete Fourth Metatarsal and Arches in the Foot of Australopithecus afarensis. Science 331: 750-753
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