THE AUSTRALOPITHECINES

=The Australopithecines= The australopithecines are the earliest Hominin ancestors that show show definite evidence of bipedalism. They possessed a gracile (less robust) body form and were '''scavengers'''; opportunistic omnivores, scavenging meat from carcasses and feeding off a wide range of resources. They originated in East Africa but later reached South Africa. Some australopithecine species have even been found in Chad, Central Africa, suggesting covered a relatively wide range. [image:http://i.imgur.com/nstw435.png] While the Australopithecines were definitely bipedal, many scientists believe that Australopithecus anamnesis (the oldest of the australopithecines) still often climbed trees. Tree climbing was one behaviour that was probably retained by early Hominins until the appearance of the first Homo species about 2.5 million years ago. A set of footprints has been found in Laetoli, Tanzania where two early hominids once walked along the shore of an ancient lake around 3.6 million years ago. These footprints were preserved in volcanic ash and most likely belong to an early Hominin such as LUCY (Australopithecus afarensis). The hominid prints were produced by three individuals, one walking in the footprints of the other, making the original tracks difficult to discover. The footprints demonstrate that the hominids walked upright habitually, as there are no knuckle-impressions. The feet do not have the mobile big toe of apes; instead, they have an arch typical of modern humans. The hominids seem to have moved in a leisurely stroll and may not have yet be capable of running at a faster pace. =''Australopithecus anamensis''= [image:http://i.imgur.com/EYxHwSa.png?1] Anamensis existed about 4 million years ago, and has a mixture of primitive features in the skull, and advanced features in the body. The teeth and jaws are very similar to those of older fossil apes. A partial tibia (the larger of the two lower leg bones) is strong evidence of bipedality, and a lower humerus (the upper arm bone) is extremely humanlike. '''Key Features''': • Relatively primitive, ape-like teeth • Tibia (leg bone) strong evidence of bipedalism (but also climbed trees) =''Australopithecus afarensis'' (LUCY)= [image:http://i.imgur.com/LVwzusR.png?1] A. afarensis existed between 3.9 and 3.0 million years ago. A most remarkable find of a relatively complete (approx 40%) skeleton has helped scientists to draw a clearer picture of what these early human ancestors looked like. Because the skeleton was so complete, Donald Johanson, its discoverer, suspected it was female right from the beginning, nick-naming the find Lucy after a Beetles song that was playing at the time. The '''pelvis and leg bones''' far more closely resemble those of modern man, and '''leave no doubt that they were bipedal''' (although adapted to walking rather than running). Females were substantially smaller than males, a condition known as sexual dimorphism. Height varied between about 107 cm (3'6") and 152 cm (5'0"). The finger and toe bones are curved and proportionally longer than in humans. Most scientists consider this evidence that ''afarensis'' was still partially adapted to climbing in trees; others consider it ‘evolutionary baggage’. However, the big toe appears to lack the grasping ability common to apes and the hands are similar to humans in most other details. ''A. afarensis'' also demonstrated significant sexual dimorphism; males being approx 1.7m tall with larger canines compared with only 1m tall for female. [image:http://i.imgur.com/j5kxxF2.png?2] [image:http://i.imgur.com/gvFs1NX.png?1] '''Key Ideas''': • Small, gracile, low forehead • Small brained • Skull similar to chimp except more human-like teeth • '''Pelvis and leg bones confirm they were bipedal''' =''Australopithecus africanus''= [image:http://i.imgur.com/YhkysVIl.png?6] ''A. africanus'' existed between 3 and 2 million years ago. It is similar to ''afarensis'', and was also bipedal, but body size was slightly greater. Brain size may also have been slightly larger, ranging between 420 and 500 cc. This is a little larger than chimp brains (despite a similar body size), but still not advanced in the areas necessary for speech. The back teeth were a little bigger than in ''afarensis''. Although the teeth and jaws of ''africanus'' are much larger than those of humans, they are far more similar to human teeth than to those of apes. The shape of the jaw is now fully parabolic, like that of humans, and the size of the canine teeth is further reduced compared to ''afarensis''. [image:http://i.imgur.com/bGv8Thdl.png?2] '''Key Ideas''': • Similar to afarensis • Slightly larger, with slightly larger brain • Less prominent brow ridge higher forehead and shorter face • Canines further reduced • Teeth and jaw still much larger than humans An interesting associated find was the discovery of a skull from a young ''A.africanus'' child. The skull is though to be from an individual approximately three years old who was killed by an eagle or other large predatory bird. The individual has been named the ‘Taung Child’ after the place where it was found (Taung, South Africa).