Chapter 7: Why is it important to understand when and why people became farmers?This answer MUST be from chapter 7.

"Guns, Germs, and Steel" by Jared Diamond is a history of "fates of human societies."  In chapter 7, Diamond discusses the process of domestication of wild plants, farming and the reasons farmers chose the seeds they chose to domesticate.  Diamond explains the concept of "natural selection" of wild plants to become domesticated crops because of their "size, bitterness, how much meat was in the fruit as well as the oiliness, and fiber lengths."

This concept of how and why some foods became domestic and some didn't is the main idea of chapter 7.  The chapter discusses how a mutant form of pea plant became the choice to become domesticated rather than the plant which pod's burst open to spread the seeds.  The chapter discusses the purpose of long fibers in domestication of hemp and other plants used for making thread and fabrics. 

While it is important to understand how and why we grow, harvest and eat the plants we have today I don't believe this chapter centers on what you are asking.  I honestly believe you are referring to chapter 6, "To Farm or Not To Farm."  It is in this chapter that Diamond address the true beginning of his actual thesis.  Why did some societies become disproportionately powerful?  It all began with the domestication of food and the switch from societies of hunters and gathers to societies of food producers and farmers.  The societies of farmers were denser in population.  This led to more births and larger populations which led to more needs of production.  There were more germs and more immunities which led to longer life spans and the need for more innovative ways to live and survive. 

If we don't understand the reasons surrounding when and why we became food producers, rather than hunter gatherers, we can not understand the development of our world history.  Everything begins here.