Re: Alex's gibbon-like CA
Alex Duncan (aduncan@mail.utexas.edu)
16 Nov 1995 13:24:50 GMT
In article <816468667snz@crowleyp.demon.co.uk> Paul Crowley,
Paul@crowleyp.demon.co.uk writes:
>AD> I agree that we all need to see casts, etc. My initial impression from
>AD> the pictures is that it sure looks like a abductable hallux. I guess we
>AD> all have our biases.
>
>> Altriciality and absence of tree-climbing ability are not "inconvenient
>> problems." These are issues that have been studied intensively. They do
>> not impact our ideas about the adaptations of the earliest hominids for
>> the reasons I stated above. Good science does not come from shutting
>> your eyes to inconvenient evidence. It is unfortunate that your ideas
>> are contradicted by what we know about early hominids from the fossil
>> record, but they are. Repeating baseless statements over and over again
>> won't make them any more relevant.
>
>Condemned with your own words - again.
Well, I think we see here the problem with trying to discuss something
you know nothing about. Dr. Ohman and I are on different sides of a
debate about the positional behavior of the australopithecines.
The views of Dr. Ohman's side are thus (hopefully he'll chime in here and
clarify if I make any mistakes):
1) Postcranial evidence for arboreal capacities in australopithecines
doesn't exist (but see below).
2) The evidence that does exist doesn't count.
3) On a spectrum of chimp-like and human-like anatomies,
australopithecines fall closer to the "human-like" end. Therefore, their
positional behavior was IDENTICAL to that of modern humans.
The point of view of the other side of the debate is that
australopithecine morphology really does tell us something about what
australopithecines were like. The best interpretation for a huge number
of features that look as if they would have been adaptive for tree
climbing is that australopithecines actually climbed trees, and in fact
relied on trees as places to sleep, get food, and avoid predators.
As far as the Sterkfontein foot goes, I would argue that both Dr. Ohman
and myself are biased toward our own particular points of view. Dr.
Ohman doesn't think it likely that australopithecines had opposable toes,
so he doesn't see one there. I think it very likely that australopiths
had opposable toes, based on the fact that every relevant
australopithecine bone shows evidence for an abductable hallux (IMO). As
far as I'm concerned, the Sterkfontein foot confirms my perspective.
As far as some of the other things you cited --
JO> Patently false. Please refer to Latimer and Lovejoy (1990, AJPA
JO> 82:125-134). This work has never been refuted. And your unpublished
JO> work that you mentioned in an earlier post does not count since it
has
JO> never been peer-reviewed. Therefore Australopithecus afarensis must
be
JO> viewed as NOT possessing a grasping foot.
I will not discuss Latimer & Lovejoy's work on the hallucial
tarsometarsal joint in this forum, other than to say I think they reached
the wrong conclusions.
As far as the non-peer-reviewed article Dr. Ohman mentioned -- I don't
recall ever bringing one up. He may have been referring to the article I
was a co-author on, and which he may never have read -- it was
peer-reviewed, and it was published. It unquestionably refuted other
works of Latimer & Lovejoy about the grasping capabilities of the
australopithecine foot.
In other words, your little diatribe about australopithecine climbing
capacity has picked on one tree (opposable toe) in a vast forest of
traits that indicate australopiths may have been quite adept in the
trees. I suggest that you should become a little more familiar with the
literature before you attempt to argue this particular point.
Another point -- you seem to have linked bipedalism and altriciality.
There is no evidence that these features are linked, and no morphological
reason to suspect they were. In fact, the morphological evidence argues
the exact opposite. There may be some disagreement in the PA community
about australopith positional behavior, but there is virtually none about
the australopithecine birth canal. It was roomy. There is a good
correlation in primates between birth canal dimensions and neonatal head
size. This evidence very strongly supports the notion that
australopithecine infants were precocial (as primates go).
Again, I would suggest you might want to read something besides Morgan
before you try to argue these points. You have been misinformed.
Alex Duncan
Dept. of Anthropology
University of Texas at Austin
Austin, TX 78712-1086
512-471-4206
aduncan@mail.utexas.edu
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