ANCIENT HUMAN FOOTPRINTS IN WHITE SANDS NATIONAL PARK AND THEIR LINK TO ABRUPT CLIMATE CHANGE

A multidisciplinary team of scientists recently announced the discovery of the oldest human footprints in North America. These fossilized prints were made between 23,000 and 21,000 years ago along the shores of an ice age lake that once filled the Tularosa Basin in south-central New Mexico, in what is now White Sands National Park. This finding fundamentally changes the timeline on North American human habitation – turning back the clock of human arrival in the Americas many thousands of years. What were the circumstances of this remarkable find, what allowed these footprints to be preserved and discovered, and importantly, who made them? During the late Pleistocene, full glacial conditions were interrupted repeatedly by abrupt warming events called Dansgaard-Oeschger, or D-O events. In the southwestern U.S., D-O events caused centuries-long megadroughts, which devastated spring ecosystems, lowered lake levels, affected sea-surface temperatures and ocean circulation patterns, and even triggered seismic activity. In the Tularosa Basin, lake levels dropped dramatically during D-O 2 at ~23,500 years ago, exposing an expansive lake margin. Humans and megafauna then walked across the patchwork of wet and dry ground, leaving behind footprints and trackways that were preserved in multiple sediment layers over the course of time. To date, a total of 61 footprints, mostly from teenagers and children, have been excavated from five distinct horizons that span nearly two millennia. These new discoveries, whose creation and preservation were made possible by an abrupt climatic event, confirm that humans were present in North America during the Last Glacial Maximum, adding evidence to the antiquity of human colonization of the Americas and providing a temporal range extension for the coexistence of early inhabitants and Pleistocene megafauna.