Re: Bipedalism in different substrates

From: Jason Eshleman (jae_at_ucdavis.edu)
Date: 08/01/04 

Date: 1 Aug 2004 10:38:40 -0700

Pauline M Ross <pmross@ross-software.co.uk> wrote in message news:<i0cpg0tath3efte2jtpr9h8ta9su7jb49a@4ax.com>...

[snip]

> >> That chimps can and do subsist on a terrestrial diet and some human
> >> hunter-gatherer populations can do the same indicates that there's
> >> ample ability to make a living in these environments. It's a viable
> >> niche. That's the relevence. To establish a plausible wading model
> >> that seeks to show that a proto-hominid got significantly more of its
> >> food from a foodsource obtained through wading, one needs to show that
> >> such a foodstuff exists and can be obtained with enough ease and
> >> abundance to be a viable niche. It could be, but this isn't known.
> >> Since we don't see any non-techological primate making its living in
> >> this way it provides doubt that such a niche is really available.
> >
> >Yes we do. We see bonobos feeding off aquatic fauna in streams, we see
> >w l gorillas living off aquatic vegetation in beis and we see orang
> >utans living off fruits off very wet, swampy tropical rainforest.
> >These foods are not a large part of their overall diets but it is
> >completely plausible that in the past they could have made up a
> >greater proportion.

They are not making their living off of these resources. They're
including them as a minority part of their diet. (Is fruit in a
swampy forest now an "aquatic resource?" That's a ridiculous stretch
if you want to justify that the creatures waded to "waist deep water"
to be predictably bipedal.) Why in none of these three do they not
utilize the "aquatic" resources to a greater degree? Why does it
constitute a minority of the items foraged for? This is a real
question, not incredulity. It's important if you want to say that
some previous hominid waded more that you justify why they waded more.
 If it's to get food, what food? Since it's a minority of the diet of
other "wetland" apes, why is it? Are these wetland resources actually
abundant enough such that they could be used to a greater degree? Is
the energetic return on these items sufficient for wider exploitation.
None of this has been demonstrated. Any time you propose a diet shift,
you've got to take this into consideration. It is not sufficient to be
vague. That no ape living in these "wetlands" makes larger use of
these resources is VERY important.

[snip]

> >My hypothesis is that wading through water (the most predictable
> >factor on the planet that gets extant apes moving bipedally) was a
> >significant part of the locomotor repertoire of the earliest
> >proto-hominins. Why Jason thinks this is "piss poor" is beyond me.
> >Could it be that it involves the dreaded 'a' factor and that if it
> >proved correct he'd have a great big splodge of egg on his face? I
> >think so. Jason doesn't tell us which model he favours, although he
> >has practically said that he thinks all the models are flawed too.
> >
> >The evidence is building up quite nicely.
> >
> >a) Theoretically, the most predictable conditions for an ape to move
> >bipedally with no need for support from its upper limbs at all and to
> >continue to do so for as long as the conditions prevail is, obviously,
> >in waist deep water.

And for the nth time, the selective advantage betweenthe obligate
biped and the facultative biped in "waist deep water" is...?

[snip]

> >> Actually, Norm, it was Krueger et al. whose data indicated that it
> >> wasn't the reduction but the state of hairlessness that was the issue.
> >> They noted that people with less hair to begin with show exactly the
> >> same improvement as the hairier individuals when shaving. This
> >> indicates that it isn't the reduction, but the complete removal that
> >> is the issue, else the change in performance among those who started
> >> with more hair should have been greater. Sharp and Costill's data
> >> doesn't address this at all.
> >
> >Neither Kruger et al or Sharp & Costil looked at intermediates, so we
> >simply cannot say whether intermediate hair loss - that is body hair
> >reduction at levels less than 100% - reduces drag in water.

The observation that hairier humans experience the same (not greater)
increase in performance when shaving that the less hairy individuals
experience *DOES* address intermediates. They did look at performance
in hair reduction at less than 100% by having a heterogeneous sample
of preshaved individuals. Is this too tough for you to understand or
simply too annoying to deal with? If intermediates had an advantage,
then the hairier individuals should show a greater level of
performance.

[snip]

> >
> >Very clever but can you list out the diet of any proto-hominin? Of
> >course you can't but that doesn't stop you ridiculing my refusal to
> >speculate on such details. Water-side habitats are food rich. Of
> >course our hominin ancestors could have survived there.

Diets of hominids can be investigated to provide considerably more
information than asserting that "they could have caught crabs" and
"wetlands are food rich." Diets of hominids *have* been investigated.
Certainty about them? No, but asserting "they could have caught
crabs" and believing that you've showing anything more complex than
your ability to find a few letters on your keyboard is an insult to
people who have actually spent time researching, writing and
publishing.

Waterside habitats aren't the same as getting in and moving around in
the water. What, for the 17 zillionth time, do you think it was that
they got by wading? Do try not to be vague.

"I'm vague because it doesnt' matter." -Algis.

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