In my opinion, the second main argument in "The Human Drift" is that human wandering across the planet, back and forth, has always been fueled by fear, while motivated by the search of food (as the first argument says). It is a primal fear that, if you don't eat, you will end up in someone else's stomach. Here is a nice excerpt that illustrates this argument: "Dominated by fear, and by their very fear accelerating their development, these early ancestors of ours, suffering hunger-pangs very like the ones we experience to-day, drifted on, hunting and being hunted, eating and being eaten, wandering through thousand-year-long odysseys of screaming primordial savagery, until they left their skeletons in glacial gravels, some of them, and their bone-scratchings in cave-men's lairs."
Once London establishes his main argument that hunger is the prime motivator that compels man to wander, he presents another argument that man fears death and has been trying to attain immortality by devising ways of protecting himself from it. Once the need for food has been met, man focuses his attention on creating ways to protect himself from the inevitable—death:
Man early discovered death. As soon as his evolution permitted, he made himself better devices for killing than the old natural ones of fang and claw.
Over time, the act of killing to increase territory became common:
As time passed and man increased, he drifted ever farther afield in search of room. He encountered other drifts of men, and the killing of men became prodigious.
