Final answer:
Recent research suggests that anatomically modern humans arrived in the Americas between 20,000-14,000 BP. The Bering Land Bridge and coastal migration are the main theories for this migration, supported by genetic studies.
Step-by-step explanation:
Recent research has pushed back the probable date of the first arrival of anatomically modern humans in the Americas. Most archaeologists now accept that humans arrived in the Americas between 20,000-14,000 BP. The two well-accepted theories for this migration are the Bering Land Bridge and coastal migration from Asia. These theories are supported by genetic studies, which show continuity between the earliest Americans and populations in northeastern Siberia.