>What basis do you have for your claim that they are a famine >food?  It
certainly doesn't follow from the fact that they are >available only six
months out of the year, so you must have >some other fact in mind.
since the calories required to dig out, clean, and prepare plant foods is
very considerable compared to the caloric payoff. for calories expended a
pile of eggs or a river eel will yield a much greater percentage of
calories.
having said that, it may be an issue that paleo man often went for more than
one day or two without any significant animal meal.  so any plant food
available would have to help.  but its no use quoting junk sources which do
not provide any figures on how much calories a given plant has. which yam
are u talking about? and how many calories does it have?

andrew