Between nine and fifteen thousand years ago, some scholars believe that a land bridge existed between Asia and North America that we now call Beringia. The first inhabitants of what would be named the Americas migrated across this bridge in search of food. When the glaciers melted, water engulfed Beringia, and the Bering Strait was formed. Later settlers came by boat across the narrow strait. (The fact that Asians and American Indians share genetic markers on a Y chromosome lends credibility to this migration theory.) Continually moving southward, the settlers eventually populated both North and South America, creating unique cultures that ranged from the highly complex and urban Aztec civilization in what is now Mexico City to the woodland tribes of eastern North America. Recent research along the west coast of South America suggests that migrant populations may have traveled down this coast by water as well as by land.
Researchers believe that about ten thousand years ago, humans also began the domestication of plants and animals, adding agriculture as a means of sustenance to hunting and gathering techniques. With this agricultural revolution, and the more abundant and reliable food supplies it brought, populations grew and people were able to develop a more settled way of life, building permanent settlements. Nowhere in the Americas was this more obvious than in Mesoamerica (Figure).