Re: Are the "mosaic theories" completely vaccuous?

From: deowll (deowll_at_bellsouth.net)
Date: 11/23/04 

Date: Tue, 23 Nov 2004 17:29:29 -0600

"Jim McGinn" <jimmcginn@yahoo.com> wrote in message
news:ac6a5059.0411230049.1526d08f@posting.google.com...
> nmm1@cus.cam.ac.uk (Nick Maclaren) wrote
>
>> "deowll" <deowll@bellsouth.net> writes:
>> |>
>> |> So swinging from a tree by your arms is harmed
>> |> by walking on your hind legs? Did you ever look
>> |> at a gibbon? They are the best at brachiating
>> |> and on the ground they are bipids.
>>
>> Sigh. While gibbons do walk semi-bipedally on the ground (they
>> also often use their arms in various ways), their first reaction
>> to needing to move fast or far is to leave the ground and take to
>> the trees. They are only slightly more terrestrial than sloths.
>
> I think you might be missing Deowll's point. Unless
> I'm misinterpreting him, I think he's making a very
> good point that if we consider these gibbons to be
> representative of apes in general that are in the
> processes of transitioning to being more ground-
> dwelling that it would appear, from this evidence,
> that there was no major morphological or functional
> obstacle to the adoption (adaptation) of bipedalism.
> This is not to say that it would be cheap. And it
> doesn't answer the question as to what benefits must
> have been gained (by the freeing of the hands?) that
> offset the high costs of this adaptation. But, as
> this evidence attests, there is hardly a need for
> theoretical day dreams like AAT to explain this
> transition. IOW, this evidence (gibbons walking,
> etc.) seems to indicate that the preadaptive ramp to
> bipedalism was already in existence: it's already a
> behavior that is found in apes (including our
> chimpanzee-like earliest hominid ancestors, A'piths).
> Now what imaginary shift to some magical aquatic
> phase is supposedly going to make this transition
> any more smoother than nature has already provided.
>
Agreed. The point I responded to was that being a swinger and being a bipid
clashed. My understanding is no. Being a bipid may clash with climbing and
walking all fours due to different pelvis designs being needed. This fits
with the early south African apiths being described as being gibbon like
though slightly larger.

If you want to measure how aboral an ape was look at leg length. Gibbons are
the best in the trees and they have the shortest legs. Humans are the worst
in the trees and have the longest legs. Apiths seem to vary a good deal.

I'm still stuck with an observation I made before. I'm not sure all bipids
got there exactly the same way or for exactly the same reasons. I'm not sure
all the known ones shared an ancestor that was one.

>>
>> Many animals use strange secondary methods of locomotion (typically
>> when movement is not a selective matter, or in environments they
>> rarely visit), and it doesn't have much evolutionary effect on
>> their physiology. Dogs, elephants etc. swimming is a prime example.
>>
>> If a gibbon started to become more effectively bipedal, it would
>> need longer and heavier legs (and probably lighter arms), which
>> would indeed hinder brachiation.
>
> Undoubtedly. Which is consistent with them assuming
> a terrestrial (but stationary) lifestyle. And which
> is completely inconsistent (longer and heavier legs
> [your words]) with a shift to aquaticism. Surely you
> don't dispute this, do you?

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