Lucy's pelvis

Alex Duncan (
28 Oct 1995 15:09:59 GMT

In article <46qqb9$> Thomas Clarke, writes:

>I disagree, Lucy's pelvis looks nothing like a chimp pelvis.
>The biggest qualitative change (as opposed top quantitative -
>e.g. bigger cranium) since Lucy are in the face. If you only
>look at the head, then Australopith is indeed close to chimp,
>but in post cranial bones it is relatively far.

To my eyes, Lucy's postcrania look more chimp-like than human-like. Her
humerofemoral index is intermediate between human and chimp. She (well,
A. afarensis) has long, curved phalanges on hands and feet. The manual
phalanges have pronounced ridges for the "flexor sheaths." The scapular
glenoid is cranially oriented (vs. laterally oriented in humans),
indicating arms were used frequently in overhead positions. Thoracic
reconstruction indicates a conical, rather than "barrel shaped" thorax.
As far as the pelvis goes, when viewed anteriorly it does seem more
human-like, as it is craniocaudally shortened and mediolaterally
exapanded. However, when viewed cranially, the iliac blades are
conspicuous in their dorsal orientation. In other words, the bone
surface for attachment of the gluteal musculature faces dorsally, rather
than laterally as is the case in humans. In this aspect particularly,
Lucy's pelvis resembles that of a chimp. Since the gluteal muscles are
among the primary muscles involved in extension and abduction at the hip,
and these are among the most important locomotor movements that occur at
the hip, it is not unreasonable to say that in biomechanical terms,
Lucy's pelvis is still very chimp-like.

Alex Duncan
Dept. of Anthropology
University of Texas at Austin
Austin, TX 78712-1086