Time was when archaeologists thought the first humans to inhabit the Western Hemisphere crossed a land bridge from Asia to what is now Alaska some 10,000-12,000 years ago. But subsequent discoveries in the southern tip of South America placed humans there around the same time. Hence, the "motorcycle theory"—that humans crossed Beringia, hopped on their motorcycles and vroomed to the southern tip of South America. Now? Not so much.
New evidence shifts the timeline back for human arrival in the Americas
September 29, 2016