It was a joke.
I don't think they went from following herds to rolling out fields of seeds. It was probably done in steps. They discovered seeds and planted them and when they came back around the following year they harvested the plants while at the same time still following the herds. Repeat this process enough times and you could actually get to a point when you could wait for the herd to come to you. Or pen them up and wait for your farm to harvest.
What if they come back, and some other people, or animals eat the plants?! This is obviously bad for the group of N people that planted the seed! What is a solution? The group need to have a chain of commend, and security guards! The guy on top of the commend( priest?) tell K men to stay behind to guard the field, and after some T time , the N-K men comes back. What can go wrong? The K men that left behind don` t have any food. If they use the plant as food, then they will have to wait for the seed to become a plant, but it might take too long, or too short. If it is too short, why the rest of N-K men go? If too long, then would the K men that stay starve to dead?
What is a solution? Suppose, then N-K people go for not too long, and the plant don` t take too long to grow! That way, N-K bring the meat for the K people to eat, and the K people guard the wheat for the N-K people to have bread? what do you think?
---------- Post added 06-08-2010 at 02:44 AM ----------
actually I studied this very topic in prehistoric anthropology. I can't remember all the details, but wheat farming started because in the act of going out and cutting wheat and bringing it back to camp, you would end up dropping a lot of seed.
...but if they already settle at some place, then they most likely know farming, and what seed they need. This presuppose the thing that we need to explain! What did people started to farm if there where no farming before.