The key term in London's essay is "drift." How does London develop this term and its meaning?

According to London, the quintessial force that has driven man to survive and wonder, or drift, is food. He states that man has drifted since prehistoric times in search of food:

The history of civilization is a history of wandering, sword in hand, in search of food ... 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."

He states that it is hunger, not romance or adventure, that fuels man's need to drift. - Plato