We know the earliest Americans came from the continent of Asia, and that geographical changes helped them to make their way here. Today, North America and Asia are separated by the Bering Strait, a waterway off Alaska's west coast. During the last ice age, glaciers trapped much of Earth's ocean water, causing global sea level to drop. This exposed a "land bridge," making possible migration, or movement of people for the purpose of settling in a new place. Most experts believe that Asians, perhaps following migrating herds of big game animals, walked across this bridge to North America. Some experts, however, point to evidence suggesting some people may have migrated to North America about three thousand to five thousand years before the land bridge was even exposed. In that case, the first arrivals may have entered from more than one point.
Gradually the human population spread out across the western hemisphere, from the Arctic Circle to the southernmost tip of South America.
These ancient Americans and their decedents are called Native Americans, or Indians. Over thousands of years, Native American societies settling in different regions developed a variety of distinct languages and customs. These lifestyles were forever changed when Native Americans, Europeans, And Africans came into contact with one another just five hundred years ago.
By the late fourteen hundreds, when this transatlantic encounter began, some eight to ten million people may have lived in what is now the United States. Some scholars say the figure is closer to seven hundred thousand to eight hundred thousand.
These scholars or researchers use various scientific methods to figure out the age of materials such as seeds and bones found at archaeological sites. One common method, in use since the nineteen forties, is called radio carbon dating. Levels of carbon-14, a...