Re: Bipedalism

9 Jun 1995 00:47:41 GMT

J. Moore ( wrote:
: Rl> Harry sure does remind me of my graduate days at berkeley in the '60's.
: Rl> Gorillas coming down to the ground to escape predators.

: (That would be "students coming down to the ground to escape Guardsmen",
: Ralph. ;-)

Ah! Those were the days. My wife and I were contact people for activists
coming into San Diego (location planned for the Republican National
Convention in the 1972)...

: Rl> Just how many
: Rl> instances have you seen of this action? How much do gorillas weigh? Why
: Rl> would they be so stupid as to brachiate away in fear through the trees
: Rl> when they can place their 600 pounds on the ground and intimidate just
: Rl> about any other animal besides ourselves.

: It would be odd if they did, since the only members of the troup who'd
: be light enough to count on being able move tree-to-tree are the kids.
: And Harry's "heavy ape=knuckle-walker" "light ape=bipedal" seems to
: leave us with no chimpanzees, suggesting [he said dryly] that it's not a
: correct dichotomy.

The key element may have been arboreal mobility of A. females (in the
20-30 kg range). Chimpanzees are in the 30-50 kg range.

: Rl> As for Oxnard, whom I deeply
: Rl> respect, his analysis is probably based on some multiple discriminant or
: Rl> componet analysis, which isn't really evidence but is a technique (or
: Rl> set of them ) used to shore up an hypothesis or an interpretation.
: Rl> SAgain, the question is Harry's attribution of a set of terrestrial
: Rl> adaptations more evolved than in Australos (graciles too) and Homo
: Rl> habilis. Knuckle walking is surely one adaptation to a terrestrial
: Rl> habitat, but so is bipedalism, and it stretches the meaning of either of
: Rl> these different adaptations to call one more terrestrial than the other.

: Or for that matter, to say one or the other is more specialized. If
: science was conducted as formal debate (which it all to often [and
: unfortunately so] is) I'd say you could argue either of those propositions
: equally well (either more or less terrestrial; or either more or less
: specialized), which is not to say that either is valid.

Point conceded.

: Rl> And for OH62, it would be neat if we had some decent cranial
: Rl> evidence with it. Limb proportions from fragmented postcranials are not
: Rl> the soundest evidence, given that we lack any real knowledge of such
: Rl> variation 1.8 million years ago.

: Other than knowing that what we do see of the habiline skulls shows an
: awful lot of variation there; why wouldn't we expect to see extremely
: varied creatures underneath all those variable heads? Makes that a
: particularly unfortunate period to not have more post-cranial stuff.

I think we're in agreement on this.

: Rl> An can all of the stress analyses done
: Rl> only come up with climbing as the what is being adapted to? Would
: Rl> dragging carcasses around provide the same stress patterns?

: It's an example of getting a bit too adaptionist, or perhaps getting too
: far into the bones and biomechanics to look around at the many different
: things that living primates do with their bodies. Dragging carcasses
: (or parts thereof) might, and you could make a nearly endless list of
: possibilities, starting with such likely activities as digging or
: pulling up plants. It seems far more likely in a primate with a
: generalized diet which has grown more generalized over time to have a
: suite of behaviors affecting its adaption-selection, rather than just
: the one, overriding behavior. Perhaps a more correct conclusion to such
: a stress-analysis study could be "it shows that the adaptations seen
: wouldn't hinder climbing, which might have still been a common behavior".

Perhaps I've done too many ESS analyses...

: Rl> What else was around to make those footprints at Laetoli? Sasquatch?

I'll back off that, primarily because I think A. afarensis was bipedal on
the ground, but also because I can't find my source (read in passing in
any case).

: Interesting that people who cite the lack of "Aquatic Ape" fossils as
: a negative for that hypothesis can suggest that for a period where we
: *do* have fossils, we just don't have any of the ones that made these
: prints. Leaves a big hole for counter-attacks (anyone listening, Phil?:)

: Rl> Finally, all
: Rl> of observations of chimps and gorillas are on animals living in (now)
: Rl> protected enclaves, and it is likely that their distribution over the
: Rl> past few millions of years has been far more extensive and within an
: Rl> arborial ecological niche far less broken than now (IMHO).

: They may well have also ranged more widely in more open territory than we
: now see them, and I believe we have reports of this for gorillas before
: the introduction of guns. Just as with elk and big horn sheep in the
: North American west, they may have taken to more and more remote areas,
: as opposed to the flat lands they also used to use, under pressure from
: weapons that are far more effective in open areas than what they faced
: only a couple of centuries ago.

: Rl> Nevertheless, that we debate these points is excellent, and shows
: Rl> just how weak the fossil evidence, as well as much of our
: Rl> functional analyses. Lets keep it up.
: Rl> Ralp Holloway.

: Good conclusions about the fossil record require a lot more
: "intra-anthropological cross-pollination" than some of researchers want
: to do. You see it in both "stones and bones" people and in "molecular"
: people; others usually don't make quite the same sweeping conclusions,
: so they often avoid tripping up in spite of themselves. (It might not be
: such a problem, if it weren't for some of them having arrogant attitudes
: and the whole field seemingly inspiring animosity.) Given the amount of
: relevant material, it is probably impossible to trip over your own
: tongue ocassionally (how do *I* know this? ;-) Actually, this
: newsgroup has been pretty good, as on-line forums go; hope I didn't jinx
: it by saying that.

: (BTW, my favorite parody of adaptionist theory was Boule's Cornelius,
: the chimp scientist in Planet of the Apes, who explained to the hapless
: human that apes had become more intelligent than humans because they had
: four hands, which rather obviously required more intelligence to
: coordinate, since this allowed them to manipulate objects in more complex
: ways than the poor two-handed humans. Makes perfect sense.)

: Jim Moore (

: * Q-Blue 1.0 *

Perhaps us computational types can provide some of that cross-pollenation.

Cheers (note the new homepage) --
Harry Erwin
PhD student in comp neurosci: "Glitches happen" & "Meaning is emotional"