Re: Sabretooths

Op 06-01-2008 11:05, in artikel flq95c$5co$1@xxxxxxxxxxxxxx, Mario
Petrinovich <mario.petrinovic1@xxxxxxxxxxx> schreef:

Me:
- Human brain size should be explained as that of other animals:
there are correlations with water, trees, varied diet,
varied recent evolution etc.

Mario:
No. We have UNIQUE body thermoregulation. In our system we lose
heat through our head. ...


No, no, Mario: that's savanna believers' fanatasy (you know, running
over
hot plains & radiating heat to the sky... :-D). Dean Falk (radiator
"theory") doesn't believe this herself any more I guess.
There are large blood vessels between heart & brain: the temperature of
our
blood circulation is that of our brain. In our system we lose most heat
through our body skin (& a bit through our breathing): conduction,
convection, radiation, evaporation.

I wouldn't say so. I saw some thermo-image of our body, where it
was clear that our head radiates heat.

Yes. Of necessity: less SC fat, highly important organs (cf. seals lose a
lot of body heat through their whiskers). But not *for* radiating heat.

I am not sure about that concept. We have animals that live both, in
water and on land. In water they have to have much greater
thermo-insulation.

Not necessarily "greater", but different, eg, a fur has no function in the
water, except for small semi-aquatics (that have to groomed it intensively).

This means that on land they have to radiate heat. In the
same time, they cannot radiate heat through body parts witch have to be
insulated in water. IOW, they have to have some body parts adapted *for*
radiating excess heat on land. See how much we sweat on head. I don't know
if horses and camels do the same (of course, today we only have traits of
our past condition).

I sweat as much on my back as on my head, Mario.

Also, it is clear that our head has hair.

:-D Not mine.

Of course, ; ). But the difference in men and women condition came
later (per my view).

As Elaine wrote: "Accounts of how our Plio-Pleistocene ancestors may have
lived on the savannah include bouts of strenuous activity outside the
gallery forest for hunting or digging (Hanna & Brown 1983); dogged pursuit
of swifter animals over 1 or 2 days (Carrier 1984); and bipedal trekking
after migrating herds of savannah ungulates (Sinclair cs.1986). Some of
the
even more imaginative versions appear mutually contradictory. For example,
the hypothesis of a foraging or hunting male accords ill with the meridian
theory of Wheeler that our ancestors became bipedal to minimise direct
solar
radiation at midday and retained a hairy heat shield only on top of the
head
(1984, 1988, in imitation of DHK Lee in Newman 1970 & Schmidt-Nielsen
1974:89). If we accept this reasoning, it must have been the women who
ranged over the plains at noon while the balding and bearded males rested
in the shade."

I am not very much into paleoanthropology anymore, otherwise I would
develop more my cattle-herding concept. This involves living at the edge of
water and performing "firestick farming", thus attracting cattle towards
where humans live, as one safe place for cattle, and merging the life of
humans and cattle. This, actually, ISN'T very much different (if, at all)
from the life humans are living today. So I really don't know what would be
the problem for this to be true? I mean, as I said before, under the great
influence of Byble, people got impression that today we are extremly smart,
hence in the past we were too stupid to live the kind of life we are living
today. Recent japanesee research (thankfully Japaners don't read Byble)
showed that this simply isn't true. So, I ask you Marc, why wouldn't we live
in the past the same type of life we are living today.

In that case we were still living in the trees, without tools etc.
Don't forget 5 Ma P ancestors were H ancestors. Why aren't chimps living our
type of life?

Something like Masais.

The Masaai life is very specialised & recent. No other humans live like
that.

Along with their cottages they are living in, along with spears,
fire and everything else. The difference came with agriculture, the use of
metal, and the writting. If it wasn't for this, we would still be living
like that.

We would still be living the oceanic islander life you mean.

If we lost body hair because
of AAT and the immersion of our body in water, we definitely didn't lose
it
on our head. Not that we DIDN'T lose it, we even have too much of it.
Which is quite the opposite situation from our body.

We could have lost it totally & regrown on our scalp (just as men "regrow"
beard & moustache). But when the human (& chimp) fetus becomes naked (7th
fetal month or so) this process stops at the forehead, leaving our scalp
haired. BTW, this suggests the H/P LCA (& possibly even the gr.ape LCA)
had
a naked body. All gr.apes lack underfur (which suggests the gr.ape LCA
c.16 Ma in the Tethys coastal forests lacked body hair).

I don't know about that underfur thing. This possibly could be for
different reasons. I would have to know the condition of underfur in all
primates.
But, apart from this, head hair fits nicely in the scenario where
head is abouve water, and body is below water.

??
The food is in the water, not at the surface.

If we want to explain our big brain, we simply have to compare to other
animals with big brains, no matter their thermo-regulation.
Waterside, aquatic, arboreal, omnivorous...mammals have big brains: no
wonder humans have very big brains.

We have extremly big brain. This is an extreme situation, not
seen before or after.

Not unexpected: arboreals typically have brains about twice as big as
equally large ground-dwellers, (semi)aquatic about 3 x as terrestrials.
2x3=6. --Marc

: ) Nice mathematics, but I don't think that this mutliplies that
way. I think that what I say has more sense. -- Mario Petrinovich

You think a lot, Mario.

--marc



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