Loren Cordain has talked about this on the paleodiet list.  A search by his
name (Cordain)brings up a lot of very good material at the archives found
at:http://www.paleodiet.com

I quote:
"Based upon studies of present day hunter-gatherers, our ancestors
almost certainly ate the tubers (storage roots) of many plants.   These
roots include  raw, edible rhizomes, corms etc of a wide variety of
plants.   The main tubers of agricultural man (potatoes, sweet potatoes,
yams, cassava etc) are inedible without cooking because of their high
anti-nutrient load and their storage form of carbohydrate.   These
tubers contain huge amounts of  poorly digested starch which becomes
more digestible during cooking .  Additionally many, but not all
antinutrients are denatured or reduced with cooking and/or processing
(soaking in water or leaching in alkaline solutions).   The difference
between wild edible roots and commercially available starchy tubers is
that, the starch content is generally much lower in wild roots and there
tends to be more stored sachharides and less toxic antinutrients.
Examples of domesticated roots which certainly should be a part of a
-modern paleolithic diet- would include carrots, beets, parsnips,
radishes, daikon, turnips or any other non-starchy root which is edible
and non-toxic in its raw state.   Potatoes are clearly inedible in their
raw state and there have been more than 30 deaths reported in humans in
this century from eating raw potatoes (Slanina P.  Solanine
(Glycoalkaloids) in potatoes: toxicological evaluation. Fd Chem Toxic
1990 28:759-61.)."

Ray Audette
Author "NeanderThin"
As seen on "Oprah" on Oct. 4