btw, Einstein's solution of vegetarianism assumes unlimited human access to mechanical energy and perfect recapture of nutrients. As it is, opposite to what we believed for nearly 200 years, due to the expenses of creating nutrient mediums, animals are more useful calorie sources for most of the lands west of the Mississippi, and in numerous places across the earth.
https://www.youtube.com/watch?v=vpTHi7O66pI