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Australopithecus afarensis

Australopithecus afarensis
Australopithecus afarensis is an extinct hominid species, which to some, is considered to be the "missing link" in human evolution. This is because the species shares a significant amount of traits with both chimpanzees and anatomically modern humans. 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" was unearthed from one of the most famous paleoanthropological finds in history. The potassiumargon dating found that the ancient species is thought to have lived between 3.76 and 2.9 million years ago with Lucy's remains dating to around 3.2 million years ago. The remains of A. afarensis remains so significant because it shows clear evidence that humans were bipedal before developing larger brains; opposed to the previously widespread assumption that human brains evolved before walking upright. The number of traits that it shares with both chimpanzees and anatomically modern humans (or Homo sapiens) is also very intriguing to many. The claim of discovering the potential missing link as well as the precise name of the species remains the subject of heated discussions within many scholarly circles to this date.
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. 128/129. All detailed anatomical analyses and biomechanical considerations of this joint indicate that the hominid possessing it, Australopithecus afarensis, was fully capable of upright bipedal posture and gait" [1]
The Lucy find was a singular find and relatively complete (around 40%) compared to other hominid excavations in the surrounding area. Discovered by the International Afar Research Expedition (IARE), Lucy became one of the most notable finds in the history of human biological evolution. Lucy's remains dated to just under 3.18 million years old. 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.
In 1975, Michael Bush, one of Johanson's students, found the remains of more than thirteen A. afarensis individuals buried together which seemed to be the result of a flash flood or another natural disaster. This was assumed because of the presence of a catastrophic profile rather than an attritional profile. The catastrophic profile meaning that a group of organisms were buried in close proximity because of a catastrophe rather than timerelated attrition.
The find yielded vital information about the social organization of A. afarensis: "It is clearly a mixed sample of young and old, large and small  meaning several females and several males. It looks very much like the composition of A. afarensis groups was like what we see in chimpanzees," Johanson explains. [2]1978:  Site: Footprints / Holotype Tanzania
The  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. It should be noted that a number of scholars, with Mary Leakey in particular, would prefer the official name of this species to be called Praeanthropus afarensis.1999: Lucy's Baby Dikika, Ethiopia
This was the first major find by an African scientist. Zeray Alemseged was responsible for this find in Ethiopia 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 3.313.35 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).
Like an adult A. afarensis, the Dikika baby had long, curved fingers. This suggests a good amount of time spent in trees even uggs canada outlet though there exists a great number of bipedal traits. The fossil also brings new data to the debate in the form of two shoulder blades, (or scapulae): bones previously unknown for this species. According to Alemseged, the shoulder blades of the child look most like those of a gorilla. The upwardfacing shoulder socket is particularly apelike, contrasting sharply with the laterally facing socket modern humans possess. "This," Alemseged says, "may indicate that the individual was raising its hands above its head something primates do when they climb."[3]
Although the cranium is more primitive than the Australopithecus africanus, it remains classified as a gracile Australopith instead of a chimpanzee. The hominid has a relatively small brain with an average cranial capacity of 434cc. The brain of A. afarensis was about onethird the size of the average modern human brain, or about the same size as a modern ape's brain.[4] It has an encephalization quotient of 2.5 and is quite chimpanzeelike when looking at it from behind.
The compound temporal neutral crests are responsible for a smaller brain capacity and its face is much more prognathus when compared to the Australopithecus africanus. Males also typically had large crests (called sagital crests) on top of their skulls while females did not. The sagital crests are from excessive chewing pressure from enlarged jaws and molars. [5]
Although there are many apelike morphologies, there are also a number of humanlike characteristics. A. afarensis provides the first evidence that australopiths retained a generally apelike skeletal design and body shape with the exception of lower limb features which are related to bipedalism. The posterior position of the foramen magnum also suggests bipedalsim. (McHenry,1991)[6]The canines show similar wear patterns as humans which may show a possible link between humans and Australopiths. Although the canines are a bit smaller than chimpanzees, they are bigger than other Australopiths which suggests dimorphism. There is minimal metaconid development and the cusps retain an asymmetric shape which is more chimpanzeelike. The megadontia quotient is around 1.7 and they have a shallow palate which is humanlike. Although there are humanlike characteristics,the tooth rows are more parallel and narrow which is more apelike. These discrepancies show a possible link between humanlike morphologies and apelike characteristics which is both exciting and frustrating in the attempt to find a definitive answer to human evolution.
The main differences between A. anamensis and A. afarensis relates to mandibular morphology and details of the dentition. The mandibular symphysis of A. anamensis is steeplysloping compared with the more vertical symphysis of later hominids, including A. afarensis. In some respects the teeth of A. anamensis are more primitive than those of A. the low crosssectional profiles, and bulging sides of the molar crowns) they show similarities to more derived, and temporally much later, Paranthropus taxa. Compared with A. afarensis, A. anamensis also exhibits a primitive, horizontal tympanic plate. [7]
"The large premolars of A. afarensis suggests they were frugivores, and the thick enamel on the teeth suggests they may have eaten nuts, grains, or hard fruit pies".[8]
Body size
Males average a weight of 100 lbs while females average a weight of 64lbs. This suggests that the average female weighed around 64% of the typical male. This indicates a significant amount of sexual dimorphism. Some studies have suggested that there exists such a great deal of dimorphism that it could in fact be two different species. But this has been refuted because although body sizes differ, the morphological features are continuous.
In July researchers reported that A. africanus actually had more apelike body proportions than its presumed ancestor, A. afarensis. [9]The vertebrae tend to have long, apelike spinous and transverse processes, and the vertebral bodies are intermediate in size compared with ugg boots canada the ape and human conditions. Lumbar vertebrae are wedged such that the anterior length of the body is greater than the posterior length. The upper limb of A. afarensis is shorter than a great ape of comparable mass, but long relative to humans. (Jungers, 1994). [10]