London's supporting argument can be found in the following excerpt:
It has always been so, from the time of the first pre-human anthropoid crossing a mountain-divide in quest of better berry-bushes beyond, down to the latest Slovak, arriving on our shores to-day, to go to work in the coal-mines of Pennsylvania. These migratory movements of peoples have been called drifts, and the word is apposite. Unplanned, blind, automatic, spurred on by the pain of hunger, man has literally drifted his way around the planet. There have been drifts in the past, innumerable and forgotten, and so remote that no records have been left, or composed of such low-typed humans or pre-humans that they made no scratchings on stone or bone and left no monuments to show that they had been.
With these lines, London elaborates on his main argument. Whether it is the pre-human anthropoid or the Slovak who works in coal mines, the aim is the same: subsistence. It is not money but food that drives men to wander. These drifts are almost involuntary and fueled by hunger.
Once he establishes that food is the prime reason that humans drift, London says that the second factor is fear:
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.
These lines support London’s argument that human beings are also driven by fear. This fear can also be seen in London’s main argument through the phrase “sword in hand.” When the primary need for food has been met, the next human need is protection and self-defense. London’s arguments about obtaining food and protection reflect the Darwinian theory of the survival of the fittest.
