The more I think about it, the more I am inclined to believe that
there is merit in the theory that tubers were one nutritional
factor that allowed humans to disperse widely over the planet.
Tubers, as well as rhizomes, are available in many climates,
including cool dry climates.  At the same time, the quest for fat
calories would also lure humans into cooler regions, in pursuit
of the fattier animals there.  For survival in these cool
regions, controlled use of fire would be important.  I therefore
think it likely that the use of tubers as a significant source of
calories was contemporaneous with the hunting of fat-bearing
megafauna.  I don't see it as an either/or situation.  Tubers are
also easy to cook without vessels, by roasting on a sharp stick,
for example, or by tossing onto coals.

Todd Moody
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