If you choose the ability where you start with a premade town, you cannot harvest food. Even if you have food producing areas within your realm and research Civilization (starts with Advanced farming) but you seem to lack the origional "farming" tech (ie. researching farming simply gives you farming improvments but 0 actual food are produced, presumably because +10% of 0 = 0)
Happens everytime I start a game with this advantage.
Ren