<P> Before contact with Europeans, the natives of North America were divided into many different polities, from small bands of a few families to large empires . They lived in several "culture areas", which roughly correspond to geographic and biological zones and give a good indication of the main lifeway or occupation of the people who lived there (e.g., the bison hunters of the Great Plains, or the farmers of Mesoamerica). Native groups can also be classified by their language family (e.g., Athapascan or Uto - Aztecan). Peoples with similar languages did not always share the same material culture, nor were they always allies . Anthropologists think that the Inuit people of the high Arctic came to North America much later than other native groups, as evidenced by the disappearance of Dorset culture artifacts from the archaeological record, and their replacement by the Thule people . </P> <P> During the thousands of years of native habitation on the continent, cultures changed and shifted . One of the oldest cultures yet found is the Clovis culture of modern New Mexico . Later cultures include the Mississippian culture and related Mound building cultures, found in the Mississippi river valley and the Pueblo culture of what is now the Four Corners . The more southern cultural groups of North America were responsible for the domestication of many common crops now used around the world, such as tomatoes and squash . Perhaps most importantly they domesticated one of the world's major staples, maize (corn). </P> <P> The earliest verifiable instance of pre-Columbian trans - oceanic contact by any European culture with the landmasses that geologically constitute the "mainland" of modern North America has been dated to the end of the 10th century CE--this site, situated at the northernmost extent of the island named Newfoundland, is known as L'Anse aux Meadows, where unmistakable evidence of Norse settlement was uncovered in the early 1960s . </P> <P> As a result of the development of agriculture in the south, many important cultural advances were made there . For example, the Maya civilization developed a writing system, built huge pyramids and temples, had a complex calendar, and developed the concept of zero around 400 CE, a few hundred years after the Mesopotamians . The Mayan culture was still present in southern Mexico and Guatemala when the Spanish explorers arrived, but political dominance in the area had shifted to the Aztec Empire whose capital city Tenochtitlan was located further north in the Valley of Mexico . The Aztecs were conquered in 1521 by Hernán Cortés . </P>

Since when is mexico part of north america