Ok, here is a new topic. The type specimen for
Australopithecus africanus is an immature individual. Ditto
for Homo habilis. Does this present a problem? What if Taung
is actually a robust Australopithecine?
--
Philip Nicholls "To ask a question,
Department of Anthropology you must first know
SUNY Albany most of the answer."
pn8886@thor.albany.eduFrom:
lthomas@owlnet.rice.edu (Lisa Christy Thomas)
Newsgroups: sci.anthropology.paleo
Subject: Re: Immature type specimens
LIsa Christy Thomas wrote:
Which immature type specimens are you referring to for A.
africanus and H. habilis? I was under the impression that we
had enough fossil evidence to say with some degree of
certainty that A. africanus represents the gracile line of
australopithecine. H. habilis is a bit more difficult to
establish as one species, since the fossils associated with
this taxon show a large range of anatomical variability.
Philip is referring to the Taung child, who is thought have been
under six years of age at death (the exact age is debated among
researchers). Although it is the type specimen of Australopithecus
africanus, recent reexamination of the fossil suggests that the
child may have grown up to look more like a robust
australopithecine than like a gracile. Specifically, Tobias and
Falk (1988) published a paper in the AJPA in which they pointed out
the presence of an enlarged occipital-marginal sinus system on the
Taung endocast. An enlarged O/M sinuses is a feature which some
researchers (including Dean Falk) argue is fixed trait common to
all A. afarensis and robust australopithecines. All A. afarensis
described to date show an enlarged O/M sinus (including the 444
skull), while few gracile australopithecines show this feature at
all.
While this in itself is not conclusive proof that the Taung child
was actually a robust australopithecine (researchers disagree
whether an enlarged O/M sinus is a dependable phylogenetic marker),
when considered in conjunction with the young age of the individual
at death, it may be time to question how representative the Taung
child may be of the gracile australopithecine lineage.
It seems that in most of my evolution texts both of these
species (if in fact there are only two) are discussed briefly
and then set aside in favor of the better known A. afarensis
and H. erectus.
What info do you have?
- Lisa
I am curious to know which texts you are using in your courses.
There are actually many more specimens of A. africanus available
for study than A. afarensis, all of them from the Transvaal fossil
sites of Sterkfontein, Swartkrans, Kromdraii and Makapansgat. The
Sterkfontein fossil site near Johannesburg is the richest early
hominid fossil site ever excavated, having been under continuous
excavation since, at least, the late nineteen-sixties, if not
earlier (I'm sorry, but I can't seem to find the exact date right
this moment). The site is still being excavated under the
direction of Dr. Ron Clarke of the University of the Witwatersrand.
To date there are over 500 fossils from Sterkfontein alone which
have yet to be described.
The major problem with the South African sites is that it is
difficult to absolutely date the fossils found there. The caves
are carved out of dolomitic limestone, a material which does not
readily lend itself to absolute dating techniques. Since there was
no volcanic activity in the area, K/AR dating is out of the
question, and researchers have had to rely on faunal association to
build a chronologic timeframe for the fossils.
Perhaps Richard G. Klein put it best when he wrote in his text _The
Human Career_
However, since 1959 [the year Mary Leaky found the Zinj skull
at Olduvai Gorge], the southern African sites have been
largely eclipsed by spectacular australopithecine discoveries
in east Africa.
This includes the discovery of A. afarensis at Hadar as well. So
you see, it is not that the east African fossils are better known,
just that they receive more attention, in part because of the ease
with which they can be dated using absolute radiometric techniques.
Julia T. Lewandowski
jlewando@mail.sas.upenn.edu
Department of Anthropology
University of Pennsylvania
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Hobbits is practically chickens . . . . . .