The estimated age of the footprints was first reported in Science<\/em> in 2021, but some researchers raised concerns about the dates. Questions focused on whether seeds of aquatic plants used for the original dating may have absorbed ancient carbon from the lake \u2013 which could, in theory, throw off radiocarbon dating by thousands of years.<\/p>\n Human footprints infilled with white gypsum sand at the White Sands National Park in New Mexico.<\/span>Credit: <\/span>NPS\/AP<\/cite><\/p>\n The new study presents two additional lines of evidence for the older date range. It uses two entirely different materials found at the site, ancient conifer pollen and quartz grains.<\/p>\n The reported age of the footprints challenges the once-conventional wisdom that humans didn\u2019t reach the Americas until a few thousand years before rising sea levels covered the Bering land bridge between Russia and Alaska, perhaps about 15,000 years ago.<\/p>\n \u201cThis is a subject that\u2019s always been controversial because it\u2019s so significant \u2013 it\u2019s about how we understand the last chapter of the peopling of the world,\u201d said Thomas Urban, an archaeological scientist at Cornell University, who was involved in the 2021 study but not the new one.<\/p>\n Resource Program Manager, David Bustos at the White Sands National Park in New Mexico.<\/span>Credit: <\/span>NPS\/AP<\/cite><\/p>\n Thomas Stafford, an independent archaeological geologist in Albuquerque, New Mexico, who was not involved in the study, said he \u201cwas a bit skeptical before\u201d but now was convinced.<\/p>\n \u201cIf three totally different methods converge around a single age range, that\u2019s really significant,\u201d he said.<\/p>\n The new study isolated about 75,000 grains of pure pollen from the same sedimentary layer that contained the footprints.<\/p>\n \u201cDating pollen is arduous and nail-biting,\u201d said Kathleen Springer, a research geologist at the United States Geological Survey and a co-author of the new paper. Scientists believe radiocarbon dating of terrestrial plants is more accurate than dating aquatic plants, but there needs to be a large enough sample size to analyze, she said.<\/p>\n Fossil human footprints discovered in White Sands, New Mexico likely date back to between 21,000 and 23,000 years ago, according to two lines of scientific evidence published on October 5.<\/span>Credit: <\/span>NPS\/AP<\/cite><\/p>\n The researchers also studied accumulated damage in the crystal lattices of ancient quartz grains to produce an age estimate.<\/p>\n Ancient footprints of any kind \u2013 left by humans or megafauna like big cats and dire wolves \u2013 can provide archaeologists with a snapshot of a moment in time, recording how people or animals walked or limped along and whether they crossed paths. Animal footprints have also been found at White Sands.<\/p>\n While other archeological sites in the Americas point to similar date ranges \u2013 including pendants carved from giant ground sloth remains in Brazil \u2013 scientists still question whether such materials really indicate human presence.<\/p>\n \u201cWhite Sands is unique because there\u2019s no question these footprints were left by people, it\u2019s not ambiguous,\u201d said Jennifer Raff, an anthropological geneticist at the University of Kansas, who was not involved in the study.<\/p>\n<\/p>\n
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