Australopithecus Afarensis Comparative Research Paper

Australopithecus afarensis is one the ancient hominid species. It is widely considered to be the closest ancestor of Homo, but it retained also many primate characteristics similar to those of modern chimpanzee. Thus, Austarlopithecus afarensis and modern chimpanzee can be viewed as rather close species, though there are still some differences between them.

Australopithecus afarensis was a biped of relatively small size (it is considered to be the smallest species of Australopithecus). Males were approximately 150 cm in height, and females were much smaller, rarely grew over 105-110 cm. The average weight of Australopithecus has ranged from 30-60 kg. Modern chimpanzee is on the average smaller than Australopithecus, males ranging from 90 to 120 cm in height, and females from 66 to 100 cm in height. However, chimpanzees weigh more. Males are 35-70 kg males, females 26-50 kg (Dorey, 2010).

Australopithecus had a skull similar to that of modern chimpanzee and other apes, with a low, sloping forehead, a projecting face, a flat nose, and prominent brow ridges above the eyes (Dorey, 2010). The chin was almost absent. The skulls of the males have a sagittal crest for the massive jaw bones. The cranial capacity of Australopithecus ranged on the average from 375 to 550 cc.  In principal features the skull of Australopithesus was similar to that of chimpanzee, except for a different shape and arrangement of teeth. Chimpanzee skull is also characterized by a pronounced face and a small brain dome. The skull capacity is about 275–500 cc that puts chimpanzees and Australopthecs on nearly same level of intellectual development. A similar feature is also a prominent ridge across the braincase, protruding brows, and no chin.

Australopithecus had a low slope of dental arcade that was significantly slower than that of modern chimpanzee, though their teeth were similarly arranged in a rectangular shape.  The teeth of both species are relatively large, with long canines and broad incisors.

Australopithecus had a greater tendency to molarization than the chimpanzee. However, a similar feature between the two species is the variation of dental morphology depends on sex. For instance, in both Australopithecus and chimpanzee males increased molarization is displayed, while in females it is not particularly distinguished. Australopithecus teeth were arranged in wide rows in the lower jaw, and in the upper jaw the placement of the last molar resulted in tooth rows that curved in at the back (Dorey, 2010). CP3 Honing complex is also rather similar, involving sectorial lower premolars, upper and lower canines, and a diastema.

Australopithecus had an inverted rib cage, extremely similar to that of modern chimpanzee, though chimpanzee ribs are normally more round in the front section. Like that of chimpanzee, Australopithecus spine consisted of series of cervical vertebrae, thorax, lumbar vertebrae, and pelvic (Stanford, 2013). However, Australopithecus surely had vertebral column of bipedal posture, with the convex curvature of the lumbar spine, while chimpanzee spine column shape is characteristic of quadrupeds (Lovejoy, 2005).

Australopithecus relatively long arms peculiar to most early hominid species. However, unlike those of chimpanzee, its arms were not longer than its legs due to the adaptation to bipedal movement (Stanford, 2013). Australopithecus had curved finger and toe bones that were rather similar to those of modern chimpanzee, though shorter in phalange. The thumbs and fingers had significant manipulatory capabilities, and thumbs were placed apart from the fingers.

The pelvis of Australopithecus was modified according to the specific bipedal movement. It was basin-shaped and consisted of two innominate bones (each of consisting of three more bones) and the sacrum. Unlike that of quadruped chimpanzee, Australopithecus ilium was short and broad in order to balance the gravity while walking.  For the same reason, the pelvis bones of Australopithecus were bigger than those of chimpanzee.

Australopithecus’ legs were peculiar to bipeds. Femurs were slanted in towards the knee (Dorey, 2010).  The patella was displaced outward.  The tibia had big proximal condyle indicating the shift of weight from one leg to the other while walking. The foot bones were long and curved, especially in the toes. The hallux was not completely divergent but there was a gap between it and the other toes. This proves that Australopithecus was a biped similar to humans, while chimpanzee leg anatomy is quite different due to their being quadrupedal, with a shallower arch and an opposable big toe.

Australopithecus and chimpanzee differ considerably in their locomotion. Chimpanzees move on all fours and usually use their knuckles while walking. Australopithecus’ footprints prove its bipedal locomotion by the shape of the foot and configuration of toes.

Chimpanzees become mature relatively early, displaying first sexual activity at the age of 8 or 9.  Australopithecus had probably similar maturity rate. This proves the relatedness of the two species.

Australopithecus was mostly herbivorous. Such diet was conditioned by their habitat, a mix of woodland and more open areas where Australopithecus could forage in the trees and on the ground (Stanford, 2013). Unlike Australopithecus, chimpanzee is essentially omnivorous, though it often prefers fruit, leaves, buds, and other plant forage.

Australopithecus lived in a wide variety of habitats, ranging from sparse woodlands and savannahs to dense forests. This characteristic feature makes them different from chimpanzees that prefer rain forests. Secondary re-growth forests and swamp forests, though sometimes they can be found also in open savannah (Dorey, 2010). Unlike Australopithecus, chimpanzee leads arboreal mode of life, this is why woodlands are more suitable habitat for this species.

Australopithecus afarensis likely lived in relatively small social groups of 10-12 individuals, including several males, females, and children. Australopithecus mating system was characterized by low intensity of male competition (Dorey, 2010).  Since sexual bimorphism in Australopithecus was rather low, monogamous mating system was possible.

Australopithecus probably used simple tools found in the immediate surroundings. They included sticks, stones, and various plant materials but there is no proof that these tools were modified, re-shaped or otherwise adjusted to specific kinds of work. Like Australopithecus, chimpanzee is a highly social animal living in unit groups. The number of individuals in each group ranges from 40 to 60. During migration chimpanzee communities split into smaller units, each one amounting up to 10 animals. Chimpanzees are characterized by several mating patterns. The dominant female of the community can be accompanied by several males, or one male can show possessive behavior towards her. The third pattern is consort, meaning that a female and a male retire to a peripheral part of the community range.

Chimpanzees, like Australopithecus, are relatively good at using tools. They use stones, twigs, stems and other natural objects for different tasks associated with finding forage, cleaning themselves, and other vital issues (Stanford, 2013).  Overused tools are usually replaced with new ones. Similar social organization and capabilities of tool usage are accounted for by nearly same size of brain and closely related physical build of Australopithecus and chimpanzee. For instance, curved human-like hands with long flexible fingers enabled them to use the same tools with similar effect.

As a conclusion it is possible to state that Australopithecus afarensis and modern chimpanzee are rather similar in many physical and social respects. However, ecological adaptation and anatomical changes leading to bipedalism raise Australopithecus over the average primate level and bring this species in closer relationship with the humans.

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