Discovery of human footprints at White Sands, New Mexico, dated to between 21,000 and 23,000 years ago, was a notable step in understanding the initial peopling of the Americas, but that work was met with criticism focused on the reliability of the materials used in the radiocarbon dating: seeds of the common aquatic plant Ruppia cirrhosa and conifer pollen grains. A new study led by University of Arizona researcher Vance Holliday marks the third...
