Working my way through this. Interesting so far, my only objection so far is that you mention fruit only being available part of the year when it is in season, but this depends on where you live. In Latin America or parts of the world close to the equator, fruit is ripe most of the year naturally. Banana for example doesn't have a season, it just grows all the time. 

 Our brains grew more than any other time as a species during the ice age, when there were zero plants to eat anywhere

Just because they exist, doesn't mean we are supposed to eat them. The Stephen Thomas episode I linked above dives into that more 

 Cool, I missed that there were two links. I'll check it out!