The Age of Nationalism

Indeed, it could be argued that the age of nationalism actually is a product of the human condition.
ALL THIS debate over how best to define our time brings us back to the nation-state. Over the entire history of human organization, from bands of hunter-gatherers to the international institutions of today, its emergence is one of the most important developments of humankind. Those international-relations courses that drill into students the concept of Cold War bipolarity also teach them that the modern nation-state was born in the mid-seventeenth century. The birth certificate was the Peace of Westphalia of 1648, which marked the end of the religion-driven Thirty Years’ War and codified the concept of state sovereignty. What is sometimes called the Westphalian system is reflected in the clean lines drawn between states on today’s world map.
http://nationalinterest.org/article/the-age-nationalism-8954?page=1