A key shift that led to the development of nationalism is the disconnect between conceptions of cosmology (the history of the universe) and the history of human beings.
Before the scientific revolution, peoples around the world—including those in Christian Europe—believed that the physical universe served merely as a stage for human history.
The Christian Bible, for example, describes the Earth as the center of creation and as 6,000 years old.
Today, on the other hand, scientists believe Earth to be 4.5 billion years old. Science also indicates that humans have occupied the planet for 0.004 percent of that time.
These beliefs are still controversial in the United States. For example, in 2012 presidential candidate Marco Rubio initially claimed that
"Whether the Earth was created in 7 days, or 7 actual eras, I'm not sure we'll ever be able to answer that. It's one of the great mysteries."
Wikipedia offers a good basic time line of life of Earth.
From the Washington Post. Click to enlarge.
200,000 BC: Archaeologists have discovered 200,000-year-old human skeletons that are identical to those of modern humans. Earlier remains show enough differences to be categorized as something other than "homo sapiens."
50,000 BC: Archaeology also suggests that a major transformation in our species occurred about 50,000 years ago, when humans achieved "behavioral modernity." Most believe that these new abilities for complex thought and expression are tied to the development of language.
8,000 BC: For all of these 192,000 years, humans lived together in small, hunter/gather groups. (This has huge implications for our understandings of human community, as a recent study suggests.) Much more recently, another fundamental change occurred, when humans discovered agriculture. The next slide focuses on history since this "Neolithic Revolution."
The "Neolithic Revolution" occurred around 8000 years BC. Humans developed agriculture, and for the first time, therefore, people did not have to live near sources of food. As a result, cities began to develop.
For roughly the next 9,500 years, two social formations regulated the broader societies enabled by this transformation: religious communities and dynastic realms.
Only during the last 600 years or so has one's "nationality" been available as a organizing identity. This is nationalism, and Benedict Anderson argues that this powerful new form of self-understanding was made possible only by the combination of a new technology and an emerging economic system.
This is Print Capitalism.