Lake levels and trackways: An alternative model to explain the timing of human-megafauna trackway intersections, Tularosa Basin, New Mexico

Abstract

The margins of Paleolake Otero in southern New Mexico, USA, contain one of the largest concentrations of fossilized late Pleistocene (Rancholabrean) megafauna trackways in North America. These fossil footprints include tracks of Ice Age proboscideans, ground sloth, dire wolf, and camelids, as well as humans. Biomechanical interpretations of these fossil footprints suggest that prehistoric people in the basin regularly interacted with the megafauna. However, these trackway studies employ a geomorphic context that assumes an unlikely static landscape that changed very little after the human–megafauna interaction occurred during much of the terminal Pleistocene to the latest Holocene. In this study, we present a new lacustrine paleoclimate record from the western margin of Paleolake Otero to demonstrate that the lake underwent six developmental phases as lake levels waxed and waned at the end of the last Ice Age, reflecting a dynamic shoreline. We also reconcile how different factors have complicated the currently proposed timing of these human–megafauna trackway intersections; namely, the lake is now thought to have persisted during the terminal Pleistocene longer than previously thought, and multiple older pre-Ice Age trackways are thought to have been exhumed by Holocene wind erosion. Finally, we propose an alternative model that states that the human trackways are not contemporaneous with nearby megafauna trackways, but simply reflect humans crossing over re-exhumed, and much older, trackway surfaces.