Whenever evolutionary changes are discussed here, it is always about the
changes that may or may not have taken place after the beginning of
agriculture.  It is assumed that Paleolithic man had completely evolved
into a carnivore, or at least had evolved a body meant for injesting huge
amounts of animal flesh with occasional vegitable matter.  But I question
that he ever completely evolved as such.  Maybe he was still in an early
stage of evolving into a meat eater.
        It wasn't all that long, maybe a million years, before that hominids were
mostly vegitarian like other primates, and only ate occassional bugs and
worms and such.  The diet consisted of roots, leaves, berries, seeds, nuts,
flowers, etc.  Most of his energy needs were met with carbohydrates, and
his fiber intake was tremendous.  The vegitable matter he injested was
nothing like the refined domesticated plant foods at the supermarket today,
which has been selected for with lower fiber and more sugar and starch and
fat in mind.
        Isn't it likely that as man evolved the mental capacity and physical
characteristics to be able to hunt animals that before were elusive to him,
that his body evolved to not only be able to utilize meat, but also
retained the ability to utilize all those foods that made up his diet
before?  Surely he could have just added those enzymes and processes
necessary to metabolize meat, with losing the ability to live off a plant
diet.  So when agriculture began, man already had the metabolic means to
live well off a diet in an agricultural economy.
        I don't think there is any question that man had only incompletely evolved
into a carnivore.  His teeth are not very different from vegitarian apes.
They have none of the characteristics of carnivores.  And for all the talk
here about the relative size of brain to digestive system length, the
length of the intestines of man is more like those of vegitarian primates
than those of canines or felines.  He still retained the attraction for
sugars and starches.  Try feeding an apple to a lion....the lion doesn't
think of it as food.  But plant foods are attractive to man.  The first
enzymes to work on our food is amylase to start carbohydrate breakdown in
the mouth.  Certainly this enzyme didn't come about in man in the last
20,000 years.
        In short, I feel man is the product of quick changes in environment in the
past million years and has retained the ability to be herbivore or
carnivore but is best being somewhere in between these extremes.  In fact
it seems we retain a requirement for a lot of fiber, and if we don't get it
there are definitely health consequences.  We don't get enough, and without
supplemental fiber a diet high in modern animal protein is almost surely
low in fiber.  Supplemental fiber, with all other things staying the same,
lowers cholesterol, lowers triglycerides, lowers LDL, raises HDL, decreases
colo-rectal cancer, decreases breast cancer, decreases pancreatic cancer,
and helps in constipation and loose bowels and irritable bowel sydrome.
Clearly we don't get enough fiber in our diets.  Our digestive system, on
it's way to evolving ways to utilize more meat, did not lose it's need for
plant foods.
Paul Getty
Morehead City, NC
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