> I suspect that for millenia our ancestors ate lean meat and body organs

This contradicts eating patterns of contemporary hunter-gatherers who live
under near Pleistocene ( ice age ) conditions.  Ice age megafauna contained
fat in far greater amounts than contemporary wild animals.  Ice age
megafauna survivors such as cows, pigs, sheep, goats and camels also are
capable of storing great amounts of fat - which is a legacy of their ice age
origins.  Water fowl also contain great amounts of fat and were much more
plentiful during most of the Pleistocene.

Larger animals have plenty of fat.  Often this fat is eaten by the hunters
and the lean is left for the dogs ( see Stefansson).

From pollen samples, we have learned that trees and other woody and tubular
plants were much scarcer during most of the Pleistocene.  On the remaining
grass lands, vegetable foods would have been non-existent for much of the
year.  On an all meat diet, humans must get the majority of their calories
from animal fat.  That we have survived indicates the fallacy of such
theories.

Eating high amounts of animal fats has not been shown to be a risk for
cancer of any kind.  Exposure to grains has been shown to substantially
increase risk of colorectal cancers ( grain workers being at highest risk).
Carcinogenic by-products produced by baking or roasting grains have recently
been found at 500 times the levels suspected by Swedish scientists.

Ray Audette
Author "NeanderThin"