FONT=Trebuchet MS]Australopithecines in my opinion were apes. I've researched them extensively & they don't seem to be on the way to human at all. Their pelvis is considered human-like & so it is claimed that they were full bipeds. This has numerous problems considering that most of their anatomy was essentially ape, including their ape head, upper body, fingers, toes etc. Their hip bones were flared like an ape making bipedality more difficult. Scans of the inner ear bones (for balance) of australopiths like africanus & robustus were almost identical to living apes showing that they were not habitually bipeds. My guess is that they were tree-dwellers who engaged in knuckle-walking (wrist-locking mechanism was found) & limited bipedality like living apes. Interestingly enough, apes like gibbons today walk on 2 legs all the time but no one is going to say they're evolving into humans.[/FONT]
That is not the opinion of most anthropologists. A. afarensis had many ape-like features, and probably still spent a good amount of time in the trees. However, the morphology of the foot shows that this species had lost the divergent toe seen in earlier species (like Ar. ramidus). This allows for "toeing off", which is how humans walk and is not seen in apes. Flared illia (a portion of the hip) are actually what we see in humans. It's part of what gives our pelves that bowl like shape which supports our organs. Apes don't have this, but instead have thick abdominal muscles because the weight of their organs is on their stomach because they are quadrupedal.
She also has a vulgus knee which is what we see in humans. This allows for the joint to support the weight of the entire body. Furthermore, we see the spine starting to form an S-shape, which is also needed to support upright walking. Finally, the position of the foramen magnum also supports bipedalism. These are not things seen in apes.
NOTE: Paranthropus robustus, boisei, and aethipopicus or are no longer considered austraopiths/australopithecines. They are in their own genus now.
FONT=Trebuchet MS]Homo habilis is really quite a confusing taxon because typically most of the bones are ape with few very similar to erectus. There's a homo habilis specimen known as Stw 53 & it's touted as an ancestor but lo & behold it locomoted like a baboon (as shown by it's inner ear anatomy). Homo habilis has very few substantial bones to it's name compared to the other names in the progression & I've never seen a good skeletal representation of it's anatomy post-cranially. Essentially, according to 2 paleoanthropologists, habilis an ape-like body size, ape body shape, ape locomotion, ape jaws & teeth, ape development & brain size. [/FONT]
Actually, H. hablis had a much larger brain than an ape. Chimps have an average brain size of 300cc-400cc, H. hablis sits around 600cc. And H. hablis has a decent collection of specimens, especially when compared to older taxons. Some of the most notable ones are: OH 62, KNM ER 1813, KNM ER 1805, SK 847, KNM ER 3733, OH 24, KNM ER 1470.
These specimens show the development of H. hablis from australopithecine characteristics in OH 62 to KNM ER 3733, which is now often grouped with H. erectus/ergaster because it shares many of same the traits.
It actually has the first appearance of a parabolic dental arcade, which is what we see in humans (apes have a U-shape). It also begins to lose the facial prognathism seen in previous species (i.e. flatter face). We also see the first manufactured tools with H. hablis.
FONT=Trebuchet MS]Homo erectus in my opinion seems pretty fully human. Anyone can see that by their anatomy, even some people today have such erectus features. They were also very smart because they built boats & had seafaring skills which is something I wish I could do.[/FONT]
H. erectus still doesn't have the cranial capacity of a human. On average it's behind H. sapiens by ~200cc. It also lacks defining human characteristics like a chin. It's skull is still too oblong, and it's brow ridges are far too robust for a human (we're a very gracile species). It also shows post-orbital constriction, which is not present in humans. It has a sagittal keel, which is not present in humans. It also displays facial prognathism not seen in humans. The cervical and thoracic vertebrae have a much smaller opening, indicating a smaller spinal cord (i.e. less nerve traffic= less intelligence). The femoral neck and head also have australopith/australopithecine characteristics and human characteristics. Essentially, it's hip joints are intermediate between humans and the australopiths/australopithecines.
I've heard briefly of the inner ear CT scans, but I haven't gotten a chance to read up on it yet. I believe it was a study done by Spoor, right?
