On Tue, 27 Aug 2002, Amadeus Schmidt wrote:

> I'd appreciate further comments (on topic).

Interesting essay, Amadeus.  Here are some comments.

You wrote: "'Expensive Tissue' only makes sense if the gut also
was highly active, at rest. Maybe this is the case. I think it
could be a little more active than other organs at rest because
it has to move it's contents."

I think "resting metabolic rate" does not imply that the gut is
at rest.  The gut is metabolically expensive because it is often
working hard even when the rest of the organism is resting.

"Personally I think a improved dietary quality alone can explain
the gut size reduction. We should think of the purpose of each
gut part. What is reduced in humans is the last part where
cellulose fermentation is going on in other primates. They need
it because they eat very much cellulose material (like leaves)
and need to derivate their energy from it.

"If a human get's more fruit (untrue) or more starch (true if you
think of Wrangham/tubers) cellusole processing is less necessary.
The fermenting part gut can be thrown overboard."

This seems correct.  But you add,

"Increased dietary quality from animals can hardly explain how
additional energy can come in. Game meat is a energetically a low
density food, unless it's fat."

This isn't right.  100g of elk (a typical game meat) is 111 kcal;
110g of yam is 118 kcal.  They are comparable.  I think
"increased dietary quality" should be understood to come from
*both* meats and high-density plant foods (where they were
available).  And of course whatever carcass fat was there (not
reported in USDA analysis) would be harvested as well, which only
adds to the energy density.

"My conclusion would be that DHA is not a limiting factor to
brain growth, except in diseased states like intoxication with
tFA, alcohol, excess w-6 acids, high insulin."

I think I agree with this.  There are people all around us, with
normal-sized brains and great intelligence who are the products
of a diet in which om-3 fats are quite scarce.  They don't eat
fish; they don't eat veggies; they don't eat flax oil; etc.
Whatever om-3 fat they get must come from the tiny amounts in
grain-fed meats and grain-based foods.  I'm not arguing, of
course, that this is a good thing, but it suggests that our
bodies greedily harvest every bit of om-3 from our food and
utilize it pretty well.

Todd Moody
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