Re: Time Frame: Early Hominids
Patricia Lynn Sothman (plsothma@artsci.wustl.edu)
28 Apr 1995 03:45:12 GMT
HARRY R. ERWIN (herwin@osf1.gmu.edu) wrote:
: Patricia Lynn Sothman (plsothma@artsci.wustl.edu) wrote:
: : JoeBeaver (joebeaver@aol.com) wrote:
: --trimmed--
: There was a note in Science News (April 22, page 253) that folks working
: at Sterkfontein (Berger in particular) have found that A. africanus was a
: good deal more arboreal than A. afarensis. The arms and legs seem to
: support the hypothesis that the primary locomotor adaptation was
: suspensory climbing, and the pelvis was more primitive than that in A.
: afarensis, although advanced in that direction from the apes. The dating
: is about 2.6-2.9 MY BP.
: Any clues? H. habilis is believed to have evolved from A. africanus, and
: my character database seems to support that position without these new
: data.
: --
: Harry Erwin
: Internet: herwin@gmu.edu
: PhD student in comp neurosci: "Glitches happen" & "Meaning is emotional"
I will attempt to answer this one also. My information comes from
hearing Berger's two talks in Oakland.
Sterkfontein excavations are currently under the direction of Lee
Berger. They have found a lot of post-cranial material, which displays
very interesting morphology. The information about the suspensory
adaptations come from five shoulder girdle elements recently recovered.
Those greatly increased the sample sizes. These new elements demonstrate
a unique morphology: namely, that africanus seemed to be adapted in the
shoulder region to both suspension and bipedality. The elements display
morphology commesurate with suspension like stability of the
gleno-humeral joint, large muscle attachments. Bipedality is inferred
from the more modern human-like broad inferior angle of the scapula.
The other talk he gave centered upon the tibial morphology of Stw 514.
It was found in close association with other fossils attributed to
africanus, so it is designated as africanus. From all the morphological
features that they are able to discern on this specimen except ONE, this
is very chimpanzee-like. From comparisons between 514 and AL-288-1
("Lucy"), 514 is more primitive and thus is inferred to have a locomotor
pattern that is different from afarensis. Berger questions the
phylogenetic relationship between afarensis and africanus based upon this
tibial specimen and other primitive morphologies within the new africanus
material.
As far as habilis is concerned. The ONLY specimen which has unquestioned
association between cranial and post-cranial fragments is OH 62 (there
are questions about the type specimen, OH 7, and the paratypes originally
ascribed to habilis, e-mail if you want references) found by Johanson's
team in 1986, published in Nature in 1987 (327: 205-209). This specimen
has been basically ignored by most paleanths because of its basic
weirdness. It dates to 1.7 my, craniodentally been assigned to habilis,
but postcranially demonstrates very ape-like morphology, especially in
the relative limb proportions. When comparing the forelimb and hindlimb
in a index, this specimen falls outside the range of modern humans, well
above any australopithecine. Basically OH 62 had arms almost as long as
its legs. So Berger's contention about phylogeny that habilis, or Homo,
originated from something more ape-like in locomotor patterning is not
necessarily unusual given the morphology of the only known habilis
post-crania.
Patricia L. Sothman | "a beautiful theory, killed by a
Dept. Anthropology | nasty, ugly little fact"
WASH U, St. Louis |
plsothma@artsci.wustl.edu | -Thomas Henry Huxley
|