Australopithecus afarensis is an extinct hominid species and is probably one of the better known species from the australopithecus genera, named by D. Johanson and T. White in 1978 ( Johanson et al. 1978). A. afarensis fossils have only been found in northern African regions like Ethiopia with the most extensive remains such as “Lucy” found in Hadar, making Hadar one of the most significant fossil-rich sites in Africa (Johanson 2004) A. afarensis were also found at sites such as Omo, Laetoli and Maka. The specimen remains of A. afarensis date between 3.9 to 3 million years ago, with “Lucy” being one of the youngest A. afarensis specimen from within the Hadar Formation ( Johanson 2004)

A. afarensis had an apelike face with a low forehead, a bony ridge over the eyes, an approximated cranial capacity of 380-500 cc, and a hint of visible sagittal crest. ( Kimbel W.H., D. Johanson and Y. Rak. 1994) They have a very prognathic face and receding chin with molars and pointed canines relatively small compared to other extinct great apes but still larger and pointier than those of modern human today. (Kimbel W.H., T.D. White and D. Johanson 1984) A.afarinsis eat many tubular foods such as roots, a big part of their diet contain nuts, berries and seeds. When a carcass of a dead animal is available, the hominids will scavenge, or eat it. They also eat the marrow of the bones to help the development of their cranial capacity. It is also “proposed that a key change in the evolution of hominids such as A. afarensis from the last common ancestor shared with chimpanzees was the substitution of plant underground storage organs for herbaceous vegetation as fallback foods.”(Greg Laden and Richard Wrangham 2005) However it is recently suggested that early hominid species about 3.4 mya ate meat by using stone implements to carve animal carcasses. (McPherron, S. P. et al 2010)

The skeletons of A.afarensis found at sites also give evidence of bipedalism. The pelvis and leg bones far more closely resemble those of modernir humans than the apes. The iliac blades are shorter and wider than those of the great apes, and the sacrum is positioned directly behind the hip joint. Another essential trait that indicates bipedalism would be the femur. The femur angles in toward the knee from the hip, allowing the foot to fall closer to the midline of the body and gives more balance while walking, which leave no doubt that A. afarensis were bipedal. However the finger and toe bones are curved and proportionally longer than in humans, but the hands are similar to humans in most other details (Johanson and Edey 1981). Which could be evidence showing that A. afarensis was not completely bipedal but was still adapted to climbing trees. Another evidence used to prove the bipedalism of A. afarensis would be the famous Laetoli footprints (3.56 mya)(Leakey and Hay. 1979 ). However, there have been controversies with many interpretations of the footprints. The majority believe that the footprints were made by A. afarensis, with a few who protested this idea. Some of the features of the Laetoli footprints include deep impressions showing pronounced heel strike; a developed medical longitudinal arch; and adducted big toe being parallel with the rest four toes and in front of the ball of the foot. (Leakey and Hay 1979 ) Further more, the Laetoli material was recovered at the site of Laetoli, Tanzania, about 50 km south of Olduvai Gorge, during the years between 1974 and 1979 by M. Leakey. Most of the specimens found were mostly jaws and teeth that date from 3.76-3.56mya (Leakey et al. 1976) The anterior teeth found at Laetoli are relatively large and among the most complete known for A. afarensis. The canines showed differences between sexes with females distinguished by smaller size and less tapered crowns. These dentitions differ from the chimpanzees. They showed an eruption pattern that is more hominid-like rather than chimpanzee-like.

“Her discovery marked a milestone in the study of mankind's prehistory” (Johanson 1976). Her name is “Lucy” One of the most famous specimen of A. afarensis recovered, known as A.L. 288-1 discovered at Hada, Ethiopia by paleoanthropologist Donald Johanson in November 1974. She is estimated to have lived 3.2 mya ( Johanson 1981). Her entire skeleton was 40% complete, consists of 47 out of 206 bones, including parts of upper and lower limbs, the backbone, ribs, and pelvis ( Johanson 1996) “Lucy is considered to be one of the most important and significant fossil in our understanding of human evolution since she is one of the oldest and most complete erect-walking human ancestral skeleton found to date ” (Johanson, Edey 1981). In addition, she proves that we adapted to bipedalism before increase in brain size. However there are many controversies about “Lucy” and her kind, such as: are finds like the A. afarensis just one species or is it two different species? Was Lucy bipedal or arboreal, or both? And last but not least, was Lucy indeed female, or male? There are numerous debates about the last controversy, because it is important to know wether Lucy is male or female. If Lucy were male, then the larger individual specimens found in Hadar must not be in the same species as Lucy. But if she is female, then she would represent the smaller ones of A. afarensis indicating that the larger ones are males. Häusler and Schmid are swiss researchers who believe that Lucy's pelvis “is too narrow to accommodate an australopithecine baby, therefore Lucy must be male.” (Shreeve 1995) However, Owen Lovejoy and Donald Johanson strongly disagree with this, they stated that "the Swiss study depends on estimates of neonatal head sizes in australopithecines that are themselves based on controversial estimates of adult brain sizes, all to determine whether a hypothetical infant of a vanished species could fit through a pelvis that was itself recovered in a badly crushed condition" (Shreeve 1995) There is no definite answer to this question, as it could all be the manner of interpretation. Although, most anthropologists believe that Lucy is female.

The social behaviour of extinct A. afarensis species is difficult to reconstruct however, it is eligible to compare the social structures of modern apes knowing the relative average body size between A. afarensis males and females. The female A. afarensis are commonly more gracile and smaller than males, which proves that sexual dimorphism existed in the A. afarensis species. Height varied between about 107 cm (3'6") to 152 cm (5'0"). If we could relate the relationships between sexual dimorphism and social group structures of the modern apes and compare it to A. afarensis, then it is evident that they likely lived in small groups with one dominant male in charge. (Wood B.A. 1994)

In conclusion, A. afarensis is essential and crucial to the understanding of early hominids, being able to understand A.afarensis have helped us tremendously on what our ancestors did millions of years ago. Just “Lucy” alone have revealed many important facts about the behaviour of our earliest ancestors, with one of the most important being the evidence of bipedality. As well as the Laetoli material, which shows the presence of evolutionary trends in its dentition and post-crania which brings us on the path of the modern human form.

References Cited

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Johanson, Donald C. 1976."Ethiopia Yields First 'Family' of Early Man". National Geographic 150 (1976): 791-811
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the rise of the hominids as an adaptive shift in fallback foods: Plant underground storage organs and australopith origins

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McPherron, S. P. et al. Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikika, EthiopiaNature 466, 857-860 (2010)

Sexing Fossils: A Boy Named Lucy? Author(s): James Shreeve Source: Science, New Series, Vol. 270, No. 5240 (Nov. 24, 1995), pp. 1297-1298

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