Production in adequate quantities to meet population needs. Nutritional requirements must be met in terms of calories, vitamins, minerals. Several models have been proposed that put the selective pressures into operation. Lewis Binford proposed a population pressure model. Ties back to populations tending to locate on coasts during the Mesolithic.
Populations eventually become to large for the coastal zones to handle.
There is pressure to move the excess into increasingly marginal zones where they must focus on more marginal species such as the weeds and grasses that eventually become cereal grains. Seems to hold in several areas of SW Asia and Central America, but not in others. Jane Jacobs, in her book The Economy of Cities proposes a fun model. Selective taking of the more wild ones who wreck the corral allows the more docile to breed in captivity, thereby selecting for docility. Wild plant seeds are gathered in copious quantities and stored in granaries.