As the human large intestine is so short relative to other Primates, adaptations must occure to
allow the starches found in edible raw fruits and vegetables to be converted into simple sugars
to be absorbed by the small intestine.  This deficiency of large intestine may also be expressed
by our un-primate like cravings (as noted by Goodall et al) of things both sweet and starchy.

That the sources of starches in agricultural diets inhibits the action of our naturally occuring
starch digesting enzymes only exasperates these cravings by cuting off the feed-back loop at the
small intestine and only allowing starches to be absorbed more slowly and less efficiently after
bacterial action in the large intestine.  Most people who eat a paleolithic diet report that
these cravings are greatly reduced in just a few days.

see:"The Expensive Tissue Hypothesis: The Brain and Digestive System in Human and Primate
Evolution" Current Anthropology vol. 36, #2 (April 1995) 199-221

Ray Audette
Author "NeanderThin: A Caveman's Guide to Nutrition"
http://www.sofdesign.com/neander