Mainstay yes, but they also have long eaten wheat and I have seen historians make the same point as Hanna about Mongols plundering the grain of other societies (along with horses, cattle, gold and women, of course) and recently adopting more and more the bad habits of modern Westerners, so unless you have counter evidence, then she seems to have the balance of the evidence on her side, sad as it may be.
On the other hand, recent evidence has shown that the grain-eating ancient Egyptians suffered nutritional deficiencies. Nutritional deficiencies usually do not prevent reproduction. On the contrary, agrarian societies tend to have BOTH higher rates of deficiencies AND higher rates of reproduction than hunter-gatherer societies. High levels of reproduction are a sign of ill health, not good health and less spacing between births means less time for mothers to build up nutrient levels for the next child. It's one of the curses of civilization, not evidence of beneficial adaptation.
The tendency to put on weight was to have another effect on the living conditions of Neolithic peoples. In spite of a much shorter life span, population densities grew dramatically. As women must have a certain minimum percentage of body fat to ovulate, the tendency of agricultural people to become fat resulted in women becoming pregnant at an earlier age and becoming pregnant again much sooner after giving birth. Studies of contemporary female hunter-gatherers have shown them to reach first menstruation several years later than agricultural women. Hunter-gatherer women averaged four years between births versus eleven months for agricultural women. [There is even a colloquial term for this phenomenon of getting pregnant twice in less than twelve months: "Irish twins."] As it was no longer necessary to carry infants from place to place, the natural constraints on family size experienced by nomadic hunter-gatherers were no longer in effect.
Obviously, greater populations required larger crop yields for sustenance. Methods of agricultural intensification such as the plow and irrigation were soon invented to boost yields. As these more intensive methods accelerated the exhaustion of the topsoil and populations continued to grow, new lands for cultivation had to be found. The process of colonization continued until recent history, until the civilized world became agricultural, polluted, overpopulated, and overweight.
--Ray Audette, NeanderThin
