Dating the Arrival of Humans in North America
Developed in the mid-twentieth century by Willard Libby and Jim Arnold, radiocarbon dating (used for dating organic materials) brought the chronology of North American prehistory into sharp focus. The method provided accurate ages for the deposits of organic material left behind by the last great ice sheets that covered the continent during the Pleistocene Ice Age that began approximately 1.6 million years ago. One such deposit was determined to be 11 ,400 years old. Radiocarbon was also used to date the traces (indications of their presence) left by America’s earliest human inhabitants, enabling scientists to map out the movements of people and glaciers and to investigate the interrelationships between the two. Libby’s first attempts to analyze an ancient North American site included what archaeologists call the Folsom culture.
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