Footprints in the White Sands desert of New Mexico were made by human feet around 21,500 years ago, according to more rigorous dating by a team of scientists, including some involved in the initial discovery. The 2021 findings dated the footprints to between 21,000 and 23,000 years ago and were initially met with scepticism due to the aquatic nature of the plant used for radiocarbon dating.
Critics argued that water could introduce older carbon into the plant, potentially skewing the results. To address this concern, the researchers collected conifer pollen from the same geological layer as the aquatic plant, providing a terrestrial carbon sample less prone to the same error margin as aquatic carbon. Radiocarbon dating of the pollen and optically stimulated luminescence dating of quartz found in the footprint layers yielded results consistent with the original findings.
The conifer pollen ranged from 22,600 to 23,400 years ago, and the quartz indicated exposure to sunlight around 21,500 years ago. Combining these results with the ditchgrass data provides evidence supporting the conclusion that humans were present in North America during the Last Glacial Maximum. The research enhances our understanding of the history of human migration and habitation in the region.
The team asserts that their new ages, combined with geologic, hydrologic, and stratigraphic evidence, unequivocally support the presence of humans in North America during this period, challenging earlier scepticism.