Mexico is a nation undergoing rapid change. Past characterizations of the country as rural, undemocratic, and protectionist have been replaced in the last decades of the twentieth century bydescriptions that refer to Mexico as urban, opening to democracy, and market-oriented. For a country composed mostly of peasants before the Revolution (1910—20), Mexico has undergone broad and rapid urbanization; Mexico City has emergedas one of the world's largest cities at the end of the twentieth century. Throughout most of its history, Mexico has been ruled by strongmen or a one-party system; in 1997 pressures for an open democracy are greater than ever. Under the presidencies of Carlos Salinas de Gortari (1988—94) and Ernesto ZedilloPonce de Leon (1994— ), the economy, long one of the most protectionist and statist of the nonsocialist countries, dramatically about-faced, embracing open-market policies and freetrade links with the United States and countries throughout the Americas. Mexico's history is long. Although the timing of the arrival of the first inhabitants to the Americas has been a point of major controversy among archaeologists, recent archaeological findings indicate that tribes from northeast Asia walked across what is now the Bering Straits perhaps as early as 35,000 years ago. Finding abundant wildlife these peoples gradually moved south, populating the entire Americas over the next several thousand years.