London begins this chapter by stating that the "dominant primordial beast was strong in Buck<span>," </span>meaning<span> that the primitive </span>will<span> to survive was now the primary factor in Buck's life. ... This arouses the "beast" in Buck, and he springs upon Spitz "with a fury which surprised them both."</span>
"Sumerian city-states fought each other" would be the best option from the list, since this internal division led to a collapse of power that left people without protection or a solid economy.
