What was one factor in the differing developments in the timing of food production according to Chapter 4 of Guns, Germs, and Steel?

In Chapter 4 of Guns, Germs, and Steel, Jared Diamond argues that the neolithic transition began earliest in regions that had favorable conditions for food production. The key, for Diamond, was the ready availability of plants and animals that could be easily domesticated. This started a virtuous cycle in which food production led to an increase in population that led in turn to the ability to produce more food. The surplus of food beyond what the individual raising the food needed to sustain life allowed for specialization of labor and time devoted to improving technologies such as pottery and metallurgy. Moreover, a group with a high population and better technology would gain military superiority, allowing itself to dominate its region. This gave certain societies a head start in developing advanced civilization with which other groups could not readily catch up.