The change that is relevant to your question is not that from a rural farming life to an urban office-working one, but the neolithic revolution.
In early prehistory and during the palaeolithic period, our ancestors lived as nomadic hunter-gatherers. They did nothing but hunt and gather food. When they were sated, they relaxed. Because they had no fridges, food could not be stored, so there was no purpose in "working" more than was necessary for the momentary satisfaction of hunger or repairing of tents and hunting gear.
"Laziness" can be seen as a result of the necessity of sustaining the ecosystem that the hunters were dependent upon:
Hunting results in rapidly diminishing returns – it is a risky, arduous
and time-consuming business. This is reflected in the fact that
predatory animals tend to be spectacularly lazy. Lions, for example,
sleep or doze for at least twenty hours a day, and spend another two
hours growling and grooming. They hunt for only about two hours a day.
Kalahari bushmen have similar been shown to hunt for only about six
hours a week [sic!]. 'Laziness' is a way of life for the big predator. (Tudge, 1998, p. 33)
Then, about 10.000 years ago, the first humans settled down and began agriculture. From this moment onwards, each day was filled with hard labor.
... farming changes the rules of the game. Farming manipulates the
environment with the express purpose of overcoming its natural
restraints. The more you manipulate, the more food you can produce.
The harder farmers work the more food they can produce. Laziness is
emphatically not favoured. A hunter who works twice as hard as average
may get twice as much food in the short term, but will soon come
unstuck as his prey disappears. But the farmer who works ten times as
hard as his neighbor will indeed produce ten times as much food – and
in favourable circumstances can sustain this tenfold increase
indefinitely. (Tudge, 1998, p. 33)
Motivation for paleolithic hunter-gatherers was simply the need to not go hungry. It was not something that you did not have. You either hunted or died. The very concept of motivation does not fit such a life, because action sprang directly from your basic needs. While those needs were satisfied, there was no need for action: "laziness, nomadism and sharing were all integral parts of the Aboriginal life-style" (Ward, 1988).
Hunter-gatherer life is the garden Eden that Adam was sent forth from: "thou shalt eat the herb of the field; In the sweat of thy face shalt thou eat bread". Rowley-Conwy, in his aptly titled article "The laziness of the short-distance hunter" (1984), argues that for one Mesolithic community in western Denmark at least, "farming was not adopted until problems arose with the hunter-gatherer economy".
If you want to study how problems with motivation came about, you'll need to go look at the difference between nomadic hunter-gatherer and settled farmer life.
Evolutionary psychology assumes "that our minds and bodies are adapted for an ancestral environment", and "that we suffer the consequences of poor fit between our inherited natures and many of the constructed environments in organizational society" (Nicholson, 1997).
Geary and Bjorklund (2000) think that motivation depends on the type of ability that is necessary for performance:
... much of formal education is "unnatural" in that much of what
children are taught involves tasks never encountered by our ancestors
(Brown & Bjorklund, 1998; Geary, 1995). Although humans apparently
have been using language for thousands of years, it is only in this
century that the majority of people on the planet are literate. Geary
(1995) referred to language and other evolved forms of cognition, such
as those represented in Figure 1 [nonverbal behavior, language, facial
processing, theory of mind, kin, in-group, out-group, social
ideologies, flora, fauna, movement, representation, engineering], as
biologically primary abilities, and skills that build upon these primary abilities but are principally cultural inventions, such as
reading, as biologically secondary abilities. Biologically primary
abilities are acquired universally and children typically have high
motivation to perform tasks involving them. In contrast,
biologically secondary abilities are culturally determined, and often
tedious repetition and external motivation are necessary for their
mastery. From this perspective, it is understandable that many
children have difficulty with reading and higher mathematics.
And from this perspective it is also understandable that most of us aren't very motivated to perform those of our daily chores that require biologically secondary abilities, and I would surmise that the motivation declines as we move towards abilities that build upon abilities that ... are more and more removed from our biologically primary concerns.
- Geary, D. C., & Bjorklund, D. F. (2000). Evolutionary developmental psychology. Child Development, 71, 57-65. doi:10.1111/1467-8624.00118
- Nicholson, N. (1997). Evolutionary psychology: Toward a new view of human nature and organizational society. Human Relations, 50, 1053-1078. doi:10.1177/001872679705000901
- Rowley-Conwy, P. (1984). The laziness of the short-distance hunter: The origins of agriculture in western Denmark. Journal of Anthropological Archaeology, 3, 300-324. doi:10.1016/0278-4165(84)90005-9
- Tudge, C. (1998). Neanderthals, Bandits, and Farmers: How Agriculture Really Began. New Haven: Yale University Press.
- Ward, R. (1988). Aboriginal communists. Labour History, 55, 1-8. http://www.jstor.org/stable/i27508887