Australopithecus afarensis

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Australopithecus afarensis is an extinct hominid species, which to some, is considered to be the "missing link" in human evolution. Although A. afarensis is an older species than A. africanus, it is thought to be one of the closest ancestors to the genus Homo. The monumental remains known as "Lucy" stemmed from one of the most famous paleoanthropological finds in history. The potassium-argon dating found that the ancient species is thought to have lived between 3.76 and 3.49 million years ago. This discovery of the potential missing link remains the subject of heated discussions within many scholarly circles.

Distinguished Digs

1973: AL 129-1: Knee joint Kada Hadar, Ethiopia ¹
Discovered in Hadar, Ethiopia by Donald Johanson, the angle of the proximal tibia and distal femur suggests a bipedal hominid. In addition, the bicondylar angle, deep patellar groove and lateral lip of the patellar groove suggest that it is in fact a hominid.

1974: AL 288-1: Lucy Kada Hadar, Ethiopia
The Lucy find was a singular find and relatively complete (around 40%). Discovered by the International Afar Research Expedition (IARE), Lucy became one of the most notable finds in the history of human biological evolution. The great significance of this find is mainly due to the fact that it was the first time there existed good evidence that humans were bipedal before developing larger brains.

1978: Laetoli Site: Footprints / Holotype Tanzania
The Laetoli site is located in Tanzania and is just south of Olduvai gorge. The site was being excavated by Mary Leakey and her team in 1975 when thirteen specimens of Australopithecus afarensis were discovered, including the current holotype of Australopithecus afarensis (a mandible). When returning to the site in 1978, the team uncovered over 20,000 animal tracks which included hominid footprints. The cluster of footprints found in the tuff dates from 3.76 to 3.49 million years ago.

2006: Lucy's Baby Dikika, Ethiopia
This was the first manor find by an African scientist in Ethiopia. Zeray Alemseged was responsible for this find and is equally astonishing as Lucy. This find was one of the most complete skeletons ever found, which included a scapula, and dated to around 3.31-3.35 million years old. The thyroid bone in the throat was not even fused yet which suggested a very early age of maturation (thus, the name Lucy's baby).

Physical Attributes

Cranial Relatively small brain with an average cranial capacity of 434cc. It has an "encephalization quotient" of 2.5 and is quite chimpanzee-like when looking at it from behind. The compound temporal neutral crests demonstrates a smaller brain capacity and its face is more prognathus when compared to the Australopithecus africanus. Although the cranium is more primitive than the Australopithecus africanus, it remains classified as a "gracile" Australopith instead of a chimpanzee.

Dental The canines show similar wear patterns as humans. This may show a possible link between humans and Australopiths. Although the canines are a bit smaller than chimpanzees, they are also bigger than other Australopiths which suggests dimorphism. there is minimal metaconid development but they have asymmetric shape which are more like chimpanzees. There is a megadontia quotient of 1.7 and have a shallow palate which is human-like. Although there are human-like characteristics, the tooth rows are more parallel and narrow which is more ape-like. This shows a possible link between human-like characteristics and ape-like morphologies.

Bipedal Locomotion
Evidence seen when examining pelvis structure, knee joint and foramen magnum

External Links

1 AL 129-1
2 Lucy's Baby

References

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