Re: chimps stronger than humans

On Apr 10, 7:56 am, "James Howard" <jmh.anthropogeny....@xxxxxxxxx>
wrote:
In reference to: > How does Neandertal, and Cro Magnon for that matter, fit
into

this framework? Both had very large brains in hyper-robust bodies."

I think living in cold environments requires extra DHEA.  The individuals
who could not provide sufficient DHEA to provide resistance body
temperatures, died.  Extra DHEA would provide increased growth and
development of the brain and body.   (The next text is intended as further
explanation.)  

Your whole scenario is based on a false premis, i.e., cold equals
increased growth
of brain and body. Tom has made an excellent point, he just did not
go back
far enough in time for his example. The Boxgrove Man, Homo
heidelbergensis,
was bigger, taller, stronger, and also had a very large brain, ca.
1200 cc. He lived
in a temperate interglacial climate, proven by lions and spotted
hyenas. From then
on Western European Neandertals got smaller (with St. C being a real
whimp in size,
being one of the last), so this makes your prediction of colder equals
larger just
backwards of what actually happened. Cro-Mags were another later input
from Africa
and the same cycle repeated itself.



This principle may also explain why ice age animals grew
larger.

Wrong again, Africa also lost some large Pleistocene animals during
the extiction
process.

 However, if a species is in a position whereby testosterone may
also be selected, then this increased testosterone may amplify the effects
of cold-induced DHEA.  Hence, the Neandertals exhibited exaggerated sizes,
produced, I suggest, by the early groups being concentrated in specific,
cold areas.

Nope, Neandetals favored southern, warmer, climates when available,
they
dealt with reindeer and mammoths only when they had to.


 Concentration, I suggest, causes selection for testosterone.
Since gorillas and orangutans are large and live in the tropics, I would
think their increase in size is more of a testosterone effect.

Then after chimps and gorillas split, they BOTH live in temperate
warm
climates, why did chimps not follow your predicted pattern?

 If anyone
responds to this, they will probably mention "Bergmann' Rule."  If an animal
increases in size due to extra DHEA triggered by cold and reaches a limit in
DHEA production, then the extra DHEA is used for warth at the expense of
size.  So animals farther north become smaller as a result.

Chimps and H h demonstrate that you are not correct in your
reasoning.


 (Now, to answer
another question likely to be generated by the foregoing, I think chimps are
smaller than gorillas and orangs due to increased testosterone in the
"common ancestor" of chimps and humans.

But neither g/o/pan lived in a cold climate, you have it just
backwards.
Tall humans and short ones lived in both warm and cold climates.

 That is, the female in the common
ancestor increased in testosterone which exposed the brains of their fetuses
to increased testosterone.  This began the process of producing a brain
which competed better for available DHEA.  Hence, chimps and humans produce
more testosterone than gorillas and orangs but are smaller.)  James Michael
Howard

But above you claimed "I think living in cold ....growth and
development of the brain
and body"
According to this reasoning, gorillas/orangs should also have larger
brains
than chimps, and they don't. You have a non-starter hypothesis that
explains nothing.



.

Relevant Pages

  • Re: chimps stronger than humans
    ... I do not say "cold equals increased growth of brain and body." ... that higher DHEA allows living in the cold and extra DHEA increases growth ... these groups is due to the increased male testosterone. ...
    (sci.anthropology.paleo)
  • The Mechanism of "Pruning" in the Human Brain
    ... The development of the human brain is rapid following birth, ... The large growth of a baby?s ... of neurons and synapses. ... It is my primary hypothesis that DHEA optimizes replication and ...
    (sci.med.psychobiology)
  • The Mechanism of "Pruning" in the Human Brain
    ... The development of the human brain is rapid following birth, ... The large growth of a baby?s ... of neurons and synapses. ... It is my primary hypothesis that DHEA optimizes replication and ...
    (sci.med.psychobiology)
  • The Mechanism of "Pruning" in the Human Brain
    ... The development of the human brain is rapid following birth, ... The large growth of a baby?s ... of neurons and synapses. ... It is my primary hypothesis that DHEA optimizes replication and ...
    (sci.psychology.theory)
  • The Mechanism of "Pruning" in the Human Brain
    ... The development of the human brain is rapid following birth, ... The large growth of a baby?s ... of neurons and synapses. ... It is my primary hypothesis that DHEA optimizes replication and ...
    (sci.bio.evolution)