The Evolution of Bipedalism in Lucy, the Australopithecus afarensis

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.

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).

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Figure 1-1
Map of Hadar, Ethiopia (top right hand corner) site where Lucy was found in 1973 by Donald Johanson. (

The 3.6 million years old footprints found in Laetoli, Tanzania in 1978 aid researchers to draw definite conclusions about the locomotory patterns of early hominins. There were literally thousands of footprints found that were preserved well, which included many animals but the footprints of early hominins helped researchers to understand human evolution. After careful examinations of the footprints based on estimates of strides length, cadence and speed of walking, when compared to modern humans we were able to conclude that Laetoli hominins were slow moving almost strolling fashion
with a rather short stride. (Lewis et al., 2010) Two sites in South Africa consisted evidence of foot structures of the early hominins. These foot specimens, consisted of four articulating elements from the heel to the ankle indicated that the heel and longitudinal arch were well adapted for a bipedal gait. (Lewis et al., 2010) Nevertheless, paleoanthropologists Ron Clarke and Phillip Tobias noted that the big toe was divergent unlike the hominin pattern, thus suggesting the big toe had more of a grasping ability which in return would have enabled them to more effectively live in arboreal environment. Therefore, some researchers highly believe that early hominins were not quite bipedal to the full extent but rather they did bit of both climbing and walking as their main locomotion. The East African fossils suggest a well-adapted bipedal gait because the arches in the foot had been developed but there were some differences in the ankle that imply that considerable flexibility was not highly possible. (Lewis et al., 2010) In 2011, a fossil discovered in Hadar showed that A. afarensis had arched feet and did indeed walk upright. A group of scientists made a detailed study of a fossil that showed a fourth metatarsal foot bone of A.afarensis (Ward et al., 2011). The metatarsal bone was compared with the same bone in humans, gorillas and chimpanzees and it showed that it was in geometry far closer to humans than any other species. The evidence clearly outlines the fact that A.afarensis were indeed walking and running in a way that was similar to humans. Hence, Lucy probably devoted some time in trees but she would have been running around on open land. This was a huge discovery because it meant that species around this time period were moving easily and quickly. It also allowed scientists to make the conclusion that the foot is a human like form of locomotion, thus the debate about Lucy’s ability to walk upright could now be put to a rest.

The fossil remains of the species A.afarensis were found in parts of Africa that were rich in rain forests. The indication of the fossil location defines the main reason why the early hominin species were considered tree climbers. This would not be common knowledge as many believe that areas near the Equators would contain deserts and a lack of trees. One of the main reasons believed as to why the early hominin species evolved into bipedalism
dies deeply in the habitual areas. The evolution of these species was due to the idea that African deserts did not allow for any plant growth such as trees; thus A. afarensis had to change their traveling style to bipedalism in order to travel to these areas. (BBC, 2011)

Lucy has created much excitement in the paleoanthropology field. She is indeed a significant figure because she had the most complete skeleton and opened the window to human evolution, especially the beginning of bipedalism. She was able to prove her locomotory gait by allowing scientists to thoroughly analyze her skeleton, and to investigate her species footprints and habitat which aided in drawing conclusions such as Lucy, Australopithecus afarensis were obligate bipedal, used a bit of both locomotion, tree climbing and walking. She showed scientists and researchers that she walked upright and this changed what most paleoanthropologists thought about species before then. She had a phenomenon among the public because of her skeleton. Lucy is almost complete and this allows people to envision a three and a half foot female walking upright. Even through the highly debated controversies, however Lucy would be greatly appreciated for giving the most important information a person can ever hear and her discovery would lead researchers in a path to understanding evolution especially locomotion in depth.


BBC. Science & Nature – The Evolution of Man, BBC, Homepage Web. Accessed November 12, 2012

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. and Savage, R. 1998. The
mechanical effectiveness of erect and “bent-hip, bent-knee” bipedal walking in Australopithecus afarensis. Journal of Human Evolution 35: 55-74.

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

Gardner, Robert. 1999. Human Evolution. Canada: Grolier Publishing.

Johanson, D. – Academy of Achievement Photo Credit, Academy of Achievement Main Menu Web. Accessed November 16, 2012

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

Stern, J.T., and Susman, R.L. 2005. The locomotor anatomy of Australopithecus afarensis. American Journal of Physical Anthropology 60: 279 – 317

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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