Re: Bipedalism in different substrates
From: Bob Keeter (rkeeter_at_earthlink.net)
Date: 07/23/04
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Date: Fri, 23 Jul 2004 23:12:40 GMT
"Pauline M Ross" <pmross@ross-software.co.uk> wrote in message
news:ee22g01h5qiuqrrbp5gpo3ti42l460rpfp@4ax.com...
> On Fri, 23 Jul 2004 02:50:04 GMT, "Bob Keeter" <rkeeter@earthlink.net>
> wrote:
>
> >The thing is that a bone buried away in a non-acidic sediment is simply
> >more likely to "hang around" long enough to form a cast or fossilize.
>
> True, of course.
>
> >The fact is that the fossil record for hominids is relatively flush with
> >examples compared to chimps and gorillas. Most chimps and gorillas
> >of today tend to live in much more acidic environments than your average
> >homind. Im just saying that this modern disparity might just be
reflected
> >in the fossil record as well. 8-) But you dont like that inference, do
> >you?
>
> I don't have a problem with it. I *do* have a problem with the fact
> that early hominids, at least, lived in woodland, which was (I
> presume) acidic and therefore not conducive to producing fossils. Yet
> we have a sizeable number of hominid fossils, and no ancestral chimp,
> bonobo or gorilla fossils. It still seems incredible to me that *no*
> chimp, bonobo or gorilla ancestor *ever* got washed out of their
> acidic forest and into a location suitable for fossilisation.
I think that the acid/base determination is sort of driven by the continual
decay
of layered leaves and such on the ground in a forest. In an area where
there were
trees but plenty of open spaces, I have a feeling that the overall acidity
is
probably moderated and certainly diluted by the more basic inputs from the
open areas.
It may just be that your "vision" of a woodland for our little ape-men may
be far
too close to a "closed forest". Again its one of those places where words,
at least
imprecise words like "woodland" dont do us any favor in this discussion.
I say "woodland" and I see something like a scrub forest with brush,
occasional
large trees and grassy meadows. You say woodland and you probably see
something akin to the Nigerian rain forests! My woodland might well be
close
to the open prarie in terms of acidity, yours. . . . well. . . . much
different!
The question remains, which scenario most nearly supports the relative
abundance
of hominid and chimp/gorilla fossils? Either hominids were much more
prolific than
their cousins or there was something in the environment causing the
disparity. My
bet is soil acidity, whats yours?
> >> [Pauline]The likely environment of chimps and early hominids is not
that
> >dissimilar.
> >
> >So our ancestors and chimp ancestors (after there was a difference of
> >course)
> >lived in the same kinds of environments? How do you KNOW that? Are
> >chimp and hominid fossils found next to each other? Werent we just
talking
> >and agreeing to the point that chimp fossils are much less common than
human
> >fossils?
>
> Of course we don't know that. It is a presumption that chimp, bonobo
> and gorilla ancestors lived in a similar habitat to where they live
> today, which is forest, closed woodland and (in the case of some
> chimps) relatively open woodland. This is exactly the same type of
> habitat where early hominid fossils have been found. When a fossilised
> chimp or bonobo or gorilla is identified, we will have a better idea
> of where they lived, but until then we have to make a presumption.
Some of us would take a continuum from "rain forest" on one end, to
relatively open savanna on the other and suggest that perhaps there
was significant overlap in the middle. Bipedal hominids would be
dominating the one end, and the gorillas lounging amongst the elephant
ear plants on the other. In this patently simplistic vision, chimps would
be the
"transitionary", middle ground. Unless my memory fails me, Ross most often
suggests hominid fossils in "open woodland", and "open forests", not the
closed forests that would be equivalent to modern gorilla haunts.
> So why are there no fossils of ancestral chimps, bonobos and gorillas?
> Possible reasons:
> 1) The hominid forests and woodland was less acidic than the
> chimp/bonobo/gorilla forests and woodland (your preference);
And less acidic would be because. . . . . fewer trees further apart?
> 2) The hominids were closer to the water sources where fossils were
> likely to be laid down (my preference);
If those water sources are out in the open with plenty of C4 sources around
Im with you! with maybe some minor details of difference of course. . . .
8-)
> 3) The other apes lived in another part of Africa altogether where no
> one has yet looked for fossils (possible);
Possible, but the obvious implication is that the "chimp and gorilla
friendly" microclimate had also "moved" to other areas.
> 4) Some of the hominid fossils are in fact ancestral to
> chimps/bonobos/gorillas (a long shot).
Maybe if you go back far enough it becomes a bit more likely, but Im
thinking that in spite of the genetic analyses we might just be talking more
in the neighborhood of 10mya.
> >I think that the big difference is the grass-fed vs grain fattened beef.
> >According to the above article "wild meat" is probably not a bad
> >Omega 3 source at all, so long as you get enough of it.
>
> OK, thanks.
But that is an important point I think. If in a "central africa" scenario,
with players somthing along the line of Sahelanthropus for example, the
need to obtain the iodine could actually drive the "appetite" and
"apptitude" for meat! Cats eat grass to get rid of hair balls, chimps
"self-medicate", and perhaps back there somewhere, where the "bad effects"
of iodine deficiency started to directly effect survival, those few aberrant
meat eating Sahelanthropines begain to take over the gene pool!
> >We, along with cattle, horses and all other mammals need trace
> >concentrations of iodine. Not a lot of course, but SOME.
>
> OK, fair enough.
Good! Iodine is off the table then?
> >>[Pauline] Read what I said: "People can survive without water for quite
a long
> >> time in extremis, but it's not feasible for day-to-day activity."
> >> People who undertake heavy work in hot conditions can die from
> >> dehydration and related heat effects if they fail to drink enough.
> >
> >And Im asking you to quantify it so that we can work my little math
> >problem. Who knows, I might just download a good topo map of
> >Kenya and get out my drawing compass! ;-)
>
> I'm sorry, I don't have time for these games. If you want to believe
> that Apiths routinely left the waterside and walked for hours across
> open country in the tropics, hunted down some kind of ungulate, and
> then walked back to the water again, presumably carrying some of the
> carcass with them - well, that's up to you. Of course, they *could*
> have done this, it's perfectly possible on an occasional basis, but if
> they had done so regularly I think it highly likely they would have
> developed a more water-conserving method of keeping cool than sweating
> away water and body salts.
Unless of course that the sweating you refer to WAS the cooling method
adopted to allow such ventures!
> >> [Pauline]Try sitting in water at 80-85 deg for any length of time
> >> and then we can talk about degrees of discomfort or chill.
> >
> >I have. If you will check you will find out that 80-85 degrees is not
> >at all unusual for the water temperature along the coast of
> >South Carolina in the summer time! 8-)
>
> You're good at maths, Bob, so work it out. If blood temperature is
> 98.4 deg and you are immersed in water at (say) 85 deg, which way is
> the heat going? Flopping in a pool in South Carolina (or anywhere with
> a proper summer) is very tolerable when your head and possibly arms
> are enjoying the baking sun and keeping you warm, but without that you
> will lose body heat.
Under natural conditions heat will always flow from the warmer to the cooler
medium. The human body runs about 37 degrees Centigrade. If you are a
scuba diver you have two good choices to keep you warm while immersed for
long periods of time. You have wet suits and dry suits. Wet suits are also
popular with surfers and kayakers. If the water temperature is above 27
degrees centigrade there is no need whatsoever for a wet suit. your body
metabolism will produce enough heat to keep you warm EVEN with natural
conduction to the water.
Here is a table from a wetsuit/drysuit manufacturer.
http://waterski.about.com/library/weekly/aa100299.htm
Wet Suit - Drysuit Temperature Chart
At what temperature should you wear a wetsuit or drysuit?
Here's a chart to help you decide.
Water How the Water What Type of
Temperature * Feels to the Body Suit to Wear
80 degrees + Bath Water None Needed
72-80 degrees Comfortable Wetsuit Trunks or Shorty
or Sleeveless
Shorty
65-72 degrees Cool at First Short John Arms / Full Leg
Wetsuit
60-65 degrees Very Chilly Full Wetsuit or Drysuit
50-60 degrees Extremely Chilly Full Wetsuit or Drysuit or Short
John
Arms / Full Leg
Wetsuit with Jacket
50 degrees
and below May Cause Shock
- use caution Full Wetsuit or
Drysuit with gloves,
hood, and
booties (if applicable)
* - degrees are in farenheit
So, at a water temperature of 80 degrees or more, even a wetsuit
manufacturer would say that "none needed". I would believe him.
You really havent been scuba diving or out in the water for extended periods
of time, have you?
Regards
bk
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