A critical assessment of claims that human footprints in the Lake Otero basin, New Mexico date to the Last Glacial Maximum

The ancient human footprints in valley-bottom sediments in Tularosa Valley, New Mexico, are fascinating and potentially important because they suggest interactions between Pleistocene megafauna as well as great antiquity. The dating of those footprints is crucial in interpretations of when humans first came to North America from Asia, but the ages have larger uncertainties than has been reported. Some of that uncertainty is related to the possibility of a radiocarbon reservoir in the water in which the dated propagules of Ruppia cirrhosa grew. As a test of that possibility, Ruppia specimens collected in 1947 from nearby Malpais Spring returned a radiocarbon age of ca. 7400 cal yr BP. We think it would be appropriate to devise and implement independent means for dating the footprints, thus lowering the uncertainty in the proposed age of the footprints and leading to a better understanding of when humans first arrived in the Americas.