GMAT Verbal Reasoning Practice Test 2

In the industrialized nations, the last century has witnessed a shortening of the average workday from twelve hours or longer to less than eight hours. Mindful of this enormous increase in leisure time over the past century, many people assume that the same trend has obtained throughout history, and that, therefore, prehistoric humans must have labored incessantly for their very survival.
We cannot, of course, directly test this assumption. However, a study of primitive peoples of today suggests a different conclusion. The Mbuti of central Africa, for instance, spend only a few hours each day in hunting, gathering, and tending to other economic necessities. The rest of their time is spent as they choose. The implication is that the short workday is not peculiar to industrialized societies. Rather, both the extended workday of 1880 and the shorter workday of today are products of different stages of the continuing process of industrialization.
Which of the following inferences about industrialization is best supported by the passage above?