Re: Are the "mosaic theories" completely vaccuous?

From: Jim McGinn (jimmcginn_at_yahoo.com)
Date: 11/23/04 

Date: 23 Nov 2004 00:49:00 -0800

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.

>
> 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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