What was the reason or reasons that people abandoned a foraging way of life and started producing their food?
This is a question that is really hard to answer because we have no records from that time period -- no one said "here is why we are going to start farming." I will give you Jared Diamond's (in Guns, Germs, and Steel) list of arguments as to why this happened:
- Wild food became less and less available. Large wild animals started to die out and so hunter-gatherers could not get as much in the way of animals.
- More domesticated plants came to be available.
- People discovered technologies that allowed them to collect, process, and store wild plants.
- As they did more of this, their population grew. As their population grew, they needed to farm more to allow more people to survive -- sort of a spiral effect.
These are Diamond's four arguments for why people started to farm.
One simple and logical reason is that it was much easier and a much more secure source of food. Foraging relies on conditions over which a person has no control, and you are in competition for that food with every other human, and every other living thing that can feed on it. So that's a pretty unreliable source for something you need to live.
A second logical reason was that since it was easier, once the technology to cultivate crops or husband domesticated animals was acquired in humans, the move to those food sources was a foregone conclusion. The path of least resistance, as it were.