Don wrote:
The fundamental idea may itself be wrong.   In Nutrition and Evolution,
Crawford and Marsh argue convincingly (I'm convinced, anyway), that humans
do not show adequate adaptation to an arid savannah environment, but show
many characteristics of adaptation to a semi-aquatic coastal life, and that
the primary evolutionary habitat of humans has been coastal areas, where in
fact most humans still live today.

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another: the requirement for iodine in the diet is hard to meet away from
the ocean.