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Re: Bidpedalism
Ralph L Holloway (rlh2@columbia.edu)
Mon, 5 Jun 1995 21:42:49 -0400
Harry sure does remind me of my graduate days at berkeley in the '60's.
Gorillas coming down to the ground to escape predators. Just how many
instances have you seen of this action? How much do gorillas weigh? Why
would they be so stupid as to brachiate away in fear through the trees
when they can place their 600 pounds on the ground and intimidate just
about any other animal besides ourselves. As for Oxnard, whom I deeply
respect, his analysis is probably based on some multiple discriminant or
componet analysis, which isn't really evidence but is a technique (or
set of them ) used to shore up an hypothesis or an interpretation.
SAgain, the question is Harry's attribution of a set of terrestrial
adaptations more evolved than in Australos (graciles too) and Homo
habilis. Knuckle walking is surely one adaptation to a terrestrial
habitat, but so is bipedalism, and it stretches the meaning of either of
these different adaptations to call one more terrestrial than the other.
There is no evidence to get the Nariokotome youth derived from KNM-ER
1470. Maybe from H. ergaster, but those are rather contemporaneous with
15000. And for OH62, it would be neat if we had some decent cranial
evidence with it. Limb proportions from fragmented postcranials are not
the soundest evidence, given that we lack any real knowledge of such
variation 1.8 million years ago. An can all of the stress analyses done
only come up with climbing as the what is being adapted to? Would
dragging carcasses around provide the same stress patterns? What else
was around to make those footprints at Laetoli? Sasquatch? Finally, all
of observations of chimps and gorillas are on animals living in (now)
protected enclaves, and it is likely that their distribution over the
past few millions of years has been far more extensive and within an
arborial ecological niche far less broken than now (IMHO). Nevertheless,
that we debate these points is excellent, and shows just how weak the
fossil evidence, as well as much of our functional analyses. Lets keep
it up.
Ralp Holloway.
On 5 Jun 1995, HARRY R. ERWIN wrote:
> Oxnard, Order of Man, Yale University Press and University of Hongkong
> Press, 1983. AL-288 and OH-62 both have hands more adapted to climbing (in
> terms of stress analysis) than Pan and Gorilla. It's also of interest that
> the Mountain Gorilla climbs _down_ to the ground and takes off
> cross-country when threatened. As I indicated, that's hardly the behavior
> of an arboreal animal. My guess is that terrestrialism is a consequence of
>
> KNM-ER 15000 is certainly the turd in the punchbowl. Except for the brain
> size (and a few details), he might fit in fairly well with the current
> population of the area. His ancestry, though, is unclear. H. rudolfensis
> (1470)? Maybe, but he doesn't fit in with most of the habilines.
>
> The problem with H. habilis is that the only well-known skeleton is
> OH-62, which has an inter-memb. ratio of 0.95 (about equal to the low end
> of Pan) and hands adapted for minimizing stress while climbing. (This is
> more adaptive than what is seen in Pan!) The knees are OK for a biped. The
> elbows of 3735 are braced against dislocation. Even more so for A.
> afarensis (except AL333 and AL333-w series) and A. africanus. See Senut
> and Tardieu in Ancestors.
>
> handle suspensory forces. Perhaps P/G are more arboreal than the gracials
> were, but that would imply that the selective forces on P/G in terrestrial
> mode are much greater than the selective forces on P/G in the arboreal
> mode, and the reverse for the gracials. I can buy that, I suppose, but
> with difficulty.
>
>
>
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