Either Norm Skrzypinski or Amadeus Schmidt posted a list of calcium rich
foods, listing of paleo foods that contain at least 50 grams of calcium per
100 gram portion.
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However many of the foods on this list would have been either inedible
without technology, or very hard to get many calories from given how small
they are and the amount of coarse fibers they contain (which can bind with
calcium, iron, magnesium and zinc).  Wild nuts are smaller and harder to
crack open than modern nuts.  Pine nuts and sunflower seeds are the
exception.

Did paleo man have a mortar and pestle for making tahini? Chia seeds, like
sesames, are very small and the fibers they contain can hinder mineral
absorption.  100 grams of such seeds would be close to one cupful.  Do you
really think that sat down and chopped on that amount of seeds in a day?
Did you ever eat an entire cup or even 3/4 cup of flax seeds in a day?  If
so, I'm surprised---many people find flax seeds indigestible and a source of
little more than methane and colonic distress!  The net calorie absorption
has got to be very small for those. Do you think they'd gather quarts of
these seedsfor a family on a regular or daily basis?  It sounds far less
appealing or practical than eating meat, marrow, fish, birds, and eggs, with
some veggies thrown in.

Skeptical,

Rachel Matesz