White Sands fossil footprints

The White Sands fossil footprints are a set of fossilized human footprints discovered in 2009 in the White Sands National Park in New Mexico. In 2021 they were radiocarbon dated, based on seeds found in the sediment layers, to between 21,000 and 23,000 years ago. If that date range is correct, they would be one of, if not the oldest record of humans in the Americas. The 61 footprints are located at the shore of an ice age era lake in the Tularosa Basin. The tracks are associated with those of extinct megafauna, such as Columbian mammoths and ground sloths.

In 2022, skeptics noted that age estimates relied on carbon dating Ruppia cirrhosa seeds, whose parent plants can intake carbon from groundwater, thereby potentially resulting in dates thousands of years too old, with a study accounting for this effect suggesting that the maximum age of the footprints is likely only 15,500–13,500 is calibrated years Before Present, comparable with many other archaeological sites across the Americas. A 2023 study that included radiocarbon dating of pollen and optically stimulated luminescence dating (OSL dating) of quartz grains within the footprint layers corroborated the original dates obtained from the seeds, though these dates have also been considered uncertain by other authors, who suggest that they represent maximum ages, rather than true age estimates, due to the OSL dating being only taken from a layer below the footprints, and the potential for old pollen to be eroded and redeposited into younger layers.