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

Abstract

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.

The Pleistocene footprints are younger than we thought: correcting the radiocarbon dates of Ruppia seeds, Tularosa Basin, New Mexico

“…If such consultation did occur, Bennett et al (2021b) did not explicitly report this detail in their supplementary materials. Regardless, Oviatt et al (2022) radiocarbon dated a modern Ruppia plant collected in 1947 from the Malpais Spring (see Figure 1A) and reported a similar δ 13 C value of −13.6‰ for the plant. Interestingly, the δ 13 C values of the seed ball and seed layers closest to Locality-2 are more enriched when compared with the modern-day isotopic baseline for Ruppia growing in the Salt Creek and Malpais Spring areas.…”

“…utilized to date the trackways were impacted by the HWE and could thus be too old and that modern Ruppia could help address the problem (Oviatt et al, 2022;Rachal et al, 2022). Bennett et al (2021a) and Pigati et al (2022b) argued that any Ruppia plants growing in the Tularosa Basin were not comparable to those that would have grown in the paleo-Lake Otero setting and that, as a result, the modern Ruppia vegetation could not be used to determine how much error had been introduced into Pleistocene seed dates by the HWE.…”

Ice and ocean constraints on early human migrations into North America along the Pacific coast

“…Several North American archaeological sites have produced possible evidence for human occupations during the LGM ( 10 , 15 , 69 , but see contrary opinions in refs. 70 and 71 ). These ages are easier to reconcile with the estimated time frames for genetic separation between Siberian and Beringian populations than the purported pre-LGM sites, but still require that humans entered the Americas prior to substantial regional deglaciation.…”

Beringia and the peopling of the Western Hemisphere

“…The recently reported discovery of footprints in sediments dating to 23–21 ka on an ancient lakeshore in New Mexico provides an unusually strong case for people in the Western Hemisphere during the LGM [82], although the dating has been disputed (e.g. [83]). If people moved into mid-latitude North America before closure of the ice-free corridor, they conceivably represent either the west Eurasian lineage in Beringia before the LGM or the East Asian lineage in Beringia during the early LGM (see below).…”