I have read D'adamo's book, and personally tried his diet for about half a
year.  I won't go into the elaboration of his technical points concerning
lectins, other than to guess Ray's definition of "foreign proteins" and
D'adamo's lectins might differ.  Proteins come in many different forms of
enzymes and amino acids.  From the book "Nourishing Traditions" by Sally
Fallon, she states:  Our primitive ancestors subsisted on a diet composed
largely of meat and fat, augmented with vegetables, fruits and nuts.  Studies
of their remains reveal that they possessed excellent bone structure, heavy
musculature and flawless teeth.  Agricultural man added milk, grains and
legumes to this diet.  These foods allowed him to pursue a more comfortable
life-style than the hunter-gatherer, but at a price.  In his studies of
primitive peoples, Dr. Price foudn that those whose diets consisted largely of
grains and legumes, while far more healthy than civilized moderns,
nevertheless had more caries than those living primarily on meat and fish.
Skulls of prehistoric peoples subsisting almost entirely on vegetable foods
have teeth containing caries and abscesses, and show evidence of tuberculosis
as well. . . . Those who had the lowest number of problems and diseases as
measured by the Cornell Medical Index had the most protein in their diet.  The
healthiest consumed an average of 125 grams per day, similar to the protein
intake of stone age man.  The claim that high protein diets cause bone loss is
supported neither by scientific research or anthropological surveys.
Inadequate protein intake leads to loss of myocardial muscle and may therefore
contribute to coronary heart disease.  However, protein cannot be adequately
utilized without dietary fats.  That is why protein and fats occur together in
eggs, milk, fish and meats. . . . Not only is it dificult to obtain adequate
protein on a diet ddevoid of animal products; such a diet often leads to
deficiencies in many important minerals as well.  This is because such a diet
will lack the fat-soluble catalysts needed for mineral absorption.
Furthermore, phytates in grains make their mineral content of calcium, iron,
zinc, and magnesium difficult to utilize.  . . . Because grains and pulses
eaten alone cannot supply complete amino acids, vegetarians must take care to
balance the two at every meal. . . . Vegetarians often have difficulty
maintaining the proper acid-alkali balance in the blood and tissues because
adequate protein and mineral s are needed for this regulation. . . .  pp.
24-27.

My guess is the quality of proteins ( a more natural balance with less
deficiencies, and less phytates to interfere with the mineral content) is why
the paleo or hunter/gatherer diet would  be a healthier diet for all humans in
general.  But this is just a layperson's guess, and I do highly recommend the
book "Nourishing Traditions", particularly the segment covering proteins.

On a personal note about my experience with D'adamo's diet, I am a Type B,
thus omnivorous according to his theory.  I supposedly can handle sugar, white
wheat flour, and dairy products.  I found I was gaining weight, eating carbs
alot and craving sweets all the time, and struggled with regularity.  However,
I am all for anyone to personally try his diet if they are curious as to how
it benefits him.  I am much happier and healthier on the Neanderthin diet, as
I am losing weight effortlessly (123 lbs easy), bp 100/70, hemocrit level 40
(iron/glucose measure that is at an excellent reading), slow pulse rate, and
can eat all I want of paleo foods!
Ella