> Isn't it likely that as man evolved the mental capacity and physical
 > characteristics to be able to hunt ..., 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? ... So when agriculture
 > began, man already had the metabolic means to live well off a diet
 >in an agricultural economy.

This confuses a couple of things and has a logical flaw.

First, as far as the NeanderThin diet goes, whether paleo man was able to
survive as a pure carnivore is almost beside the point. Paleo man was an
omnivore who ate a wide variety of meats, fruits, vegetables, nuts, and
berries, and that is the diet the book recommends for us today. Of _course_
we can still eat a lot of plant foods and thrive on them, provided we get
enough animal food as well.

The logical flaw is in equating the products of an agricultural economy with
the fruits and vegetables available to the hunter-gatherer. Agriculture made
grains, beans, potatoes, dairy products, and sugar into staples of the diet,
whereas before agriculture they had been completely unavailable, or very
nearly so. The main point of NeanderThin is that the addition of these new
foods to the diet introduced into the body large quantities of proteins it
had never learned through evolution to deal with, and all kinds of metabolic
problems resulted.

This idea is plausible to me, subject to the test of science. Biochemistry
is highly specific. Though the immune system recognizes many plant foods as
good, there is no reason to assume that it will recognize any new plant food
as good. If, as the evidence suggests, the health of agricultural peoples
declined relative to their hunter-gatherer counterparts, you have to wonder
why, and that's the beginning of scientific inquiry.