For decades, a fractious attitude prevailed over research on the earliest people in the Americas. One of the most acrimonious disputes concerned a site in southern Chile called Monte Verde, which Tom Dillehay, an anthropologist now at Vanderbilt University in Nashville, Tennessee, excavated in the 1970s and 1980s. He found evidence of human occupation1 that he dated to about 14,500 years ago. Dillehay's conclusions regarding Monte Verde put him in direct conflict with the accepted wisdom among leading archaeologists that people from Siberia did not spread across North America and venture south before around 13,000 years ago. That is the age of the Clovis culture, a group of big-game hunters who used distinctive spear points that are found littered across the United States. The Clovis people were thought to be the pioneers in North America, and many archaeologists there dismissed Dillehay's claim that Monte Verde was older.
But antagonism has faded over the past six years, as convincing evidence of pre-Clovis sites has emerged in North America (see Nature 485, 30–32; 2012). Meanwhile, South American archaeologists, who were never as sceptical as their northern colleagues, have found more sites dated between 14,000 and 12,000 years ago, indicating that hunter-gatherers had spread through South America before and during the rise of the Clovis culture in the north.The article goes on to describe how the early peoples in South America quickly spread to inhabit some of the most extreme environments--including alpine valleys high in the Andes--and established extensive trading networks.