The first inhabitants of the American continents were nomadic hunters and gathers. These nomads probably arrived in North America around 40,000 years ago, following a land bridge that formed between North America and Asia. It is believed that another group of humans migrated from Asia into North America around 12,000 years ago. Some scientits also think that some people might have used boats to follow ocean currents to the tip of South America, while others arrived following ice from Western Europe.
As these various groups traveled into the new world following wild game, they spread out across the land, forming new cultures, and in some cases, complex civilizations.
For thousands of years, these early inhabitants of the Americas made a life by hunting game and gathering food from seeds, berries and wild plants. Then, around 5000 B.C., an agricultural revolution took place near present day Mexico.