Farming is an autocatalytic process, Diamond says, because it reinforces itself. When people start to farm, they become sedentary and have larger population densities. This brings about the need for more farming to support still larger populations.
Farming societies need various technologies. When these are invented, they lead to other technologies. This leads to a situation in which a farming society has all sorts of technologies that came about in response to farming. In contrast, societies that do not start farming do not invent that original technology that reinforces itself. As time goes by, the society that does not farm will fall further and further behind the farming society in terms of technology. This is why the autocatalytic nature of farming can lead to disparities between societies.