What is the word missing from this sentence? "the ancient mesopotamians mainly relied on for food"?

The Mesopotamians mainly relied on vegetables for food. This is because for most of the meat was too expensive.
Some of their crops were barley, wheat, dates, beans, lentils, pomegranates, grapes, and nuts. And usually they only ate two meals a day, except for the rich who could afford much more. 

They traded things like information and spices, new diseases were brought over, and I imagine religious views were shared too!