Pleistocene peopling of the Americas

Our species colonized North and South America last of all the major land masses, thereby ending the spread that began a million years earlier when ancestral members of the genus Homo first ventured out of Africa. But who were the first Americans? When did they arrive? Did they come in one migration or many? How quickly and by what adaptive strategies did they move across the environmentally diverse and trackless New World? How do they relate to contemporary native Americans? We have plenty of answers to these questions. Unfortunately, we can't agree which ones are right. This much is certain: the first Americans were Homo sapiens who came from northeast Asia via the Bering Straits (Fig. 1). They may have walked from Siberia to Alaska across Beringia, the land bridge formed when vast Pleistocene glaciers froze 5% of the world's water, 1 lowering global sea levels and exposing the shallow continental shelf between Asia and America. These hunter‐gatherers were present throughout the Americas by 11,500 years ago, in time to witness the climatic and ecological changes, including the extinction of thirty‐five genera of megafauna, that signalled the end of the Pleistocene. Beyond those bare facts there is controversy. Here, then, is a brief summary of the state of the argument over the peopling of the Americas.