Final answer:
Humans probably entered much of North and South America by 10,000 BCE.
Step-by-step explanation:
The original human occupants of North and South America likely arrived from Asia sometime between 20,000 and 10,000 BCE. They spread throughout the continents, eventually developing agriculture and building urban settlements.
A recent map showing updated theories of human migration out of Africa includes major archaeological sites. Modern humans lived as hunter-gatherers in Africa, Europe, and Asia before migrating to the Americas. The populating of the Americas by Homo sapiens likely began around eighteen thousand years ago.
By around fifteen thousand years ago, human populations had expanded throughout both North and South America. This expansion could have occurred through several possible migration routes, including crossing the Bering land bridge or along the Pacific coastline of the Americas.