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From: Jeff Liebermann <jeffl@cruzio.com>
Newsgroups: rec.bicycles.tech
Subject: Re: Disc Compatibility?
Date: Fri, 07 Mar 2025 20:10:49 -0800
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On Fri, 7 Mar 2025 22:00:21 -0500, Frank Krygowski
<frkrygow@sbcglobal.net> wrote:

>On 3/7/2025 8:35 PM, Jeff Liebermann wrote:
>> 
>> Primitive man was a pyromaniac.  Whenever the necessary combustibles
>> and appropriate weather were available, primitive man would start and
>> tend a fire.  Most sources claim that the fire was mostly to keep man
>> warm during various ice ages.  However, I believe the man was
>> hypnotized by the flickering flame.
>> 
>> At some point in the distance past, man set fire to his dinner and
>> thus invented cooking.  
>
>I read an interesting article claiming that fire may have been critical 
>to evolution of humans. The claim was that cooking makes food much 
>easier to digest, and thus extract nutritional calories.
>
>Since our large brains consume an outsized portion of our calories, that 
>cooking over fire was necessary to the evolution of large brains. 
>Without cooking, the theory goes, large brained proto-humans would have 
>starved.
>
>https://pmc.ncbi.nlm.nih.gov/articles/PMC124895/
>
>"In the average adult human, the brain represents about 2% of the body 
>weight. Remarkably, despite its relatively small size, the brain 
>accounts for about 20% of the oxygen and, hence, calories consumed by 
>the body."

I don't think it's 20% oxygen (by weight) but rather is 20% sugar or
glucose (by weight):

"Sugar for the brain: the role of glucose in physiological and
pathological brain function"
<https://pmc.ncbi.nlm.nih.gov/articles/PMC3900881/>
Same as above except in easier to read PDF format:
<https://pmc.ncbi.nlm.nih.gov/articles/PMC3900881/pdf/nihms-510105.pdf>
"In humans, the brain accounts for ~2% of the body weight, but it
consumes ~20% of glucose-derived energy making it the main consumer of
glucose (~5.6 mg glucose per 100 g human brain tissue per minute)."

"It has been suggested that action potentials have been rendered
highly efficient through evolution, and thus most of the energy
consumed in the brain is used on synaptic activity"

Also, please note that oxygen, by itself, does NOT contain calories.

"Does oxygen have a calorific value?"
<https://www.quora.com/Does-oxygen-have-a-calorific-value>
"Oxygen itself does not have a calorific value because it is not a
fuel. Calorific value refers to the amount of energy released when a
substance is burned or oxidized. Oxygen is an oxidizing agent that
supports combustion; it reacts with fuels to produce energy, but it
does not contain energy that can be released on its own."

In simpler terms, the amount of energy consumed by the brain is
proportional to the amount of smoke billowing from the ears, which
explains why thinking is best performed around a fire pit.


-- 
Jeff Liebermann                 jeffl@cruzio.com
PO Box 272      http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann      AE6KS    831-336-2558