Fossilized footprints preserved for millennia in a New Mexico salt flat have provided the first direct evidence of a dramatic Ice Age interaction: humans stalking and likely hunting giant ground sloths. The tracks, discovered at White Sands National Monument, reveal a detailed story of a prehistoric pursuit, offering a rare glimpse into the behavioral dynamics between early North American people and the megafauna they lived alongside. This finding settles a long-standing question for archaeologists, confirming that humans actively engaged with these massive, clawed beasts and did not limit their hunting to mammoths and mastodons.
The discovery, published in the journal Science Advances, consists of a series of tracks where human footprints are found directly inside the much larger, apostrophe-shaped prints left by a giant sloth. This precise placement indicates a deliberate and careful pursuit, with the human hunter intentionally matching the sloth’s stride. Analysis of the sediment layers confirms that the tracks were made at the same time, ruling out the possibility that a person simply walked through the prints days or weeks later. These “ghost tracks,” which are only visible under specific moisture conditions, paint a vivid picture of a calculated encounter that was more than a chance meeting, suggesting a life-or-death drama played out on the mudflats of an ancient lakebed some 10,000 to 15,000 years ago.
A Prehistoric Drama in Footprints
The remarkable trackway was first identified a decade ago by David Bustos, a park naturalist at White Sands National Monument. However, it was a more recent investigation by a team of international researchers, including Matthew Bennett of Bournemouth University, that uncovered the full extent of the story. While excavating a set of sloth tracks, Bennett noticed a human print perfectly nestled within one. Further investigation revealed more than 10 instances of this footprint-within-a-footprint, confirming it was not an isolated incident but a sustained stalking event. The human tracker would have had to alter their natural gait to step so precisely into the sloth’s much longer stride.
These fossilized traces were left on the expansive mudflats surrounding the ancient Lake Otero. At the end of the last Ice Age, as the climate warmed, the lake began to recede, leaving behind a soft canvas that would preserve the movements of life from that era. The delicate preservation of these tracks just below the modern sandy surface provides what researchers call “fleeting evidence of behavior,” a rare form of documentation in the early archaeological record. Unlike bones or tools, which show what animals and people were present, these trace fossils record a moment of action and interaction between two different species.
Reading the Telltale Signs
Scientists were able to reconstruct the hunt by analyzing the patterns and orientation of the prints. The evidence points to a sophisticated and intentional stalking effort, not just a casual following. The key was in observing how the sloth’s behavior changed when humans were present.
Evidence of Evasion
Researchers noted that sloth tracks found in isolation tend to follow relatively straight or gently curving lines. However, the tracks that coincide with the appearance of human prints begin to zigzag, indicating the animal was actively trying to evade a pursuer. This change in movement is a strong sign that the sloth was aware of the threat and was maneuvering to escape what it perceived as a predator. The hunters, in turn, were reacting to the animal’s movements, with their own fainter tracks sometimes approaching from different directions, suggesting a coordinated effort.
The Flailing Circles
Among the most compelling evidence are features the research team has dubbed “flailing circles.” At several points along the main trackway, the sloth prints form distinct circles in the sediment, accompanied by deep claw marks. The scientists interpret these as moments when the giant sloth reared up on its hind legs, standing to its full height, and swung its powerful, clawed forelimbs in a defensive arc. This defensive posture would have been a formidable display, a last-ditch effort to ward off its attackers. The presence of these circles provides a clear indication of close-quarters confrontation.
A Formidable Quarry
The giant ground sloths of the Pleistocene were not the slow, gentle creatures we associate with the name today. These herbivores were massive, standing seven to eight feet tall when on all fours and capable of rising even higher on their hind legs. Weighing over 1,000 pounds, and in some cases more than an elephant, they were powerfully built animals. Their most fearsome feature was a set of large, wolverine-like claws on their muscular forelimbs, which were capable of tearing apart any hunter who dared a direct, frontal assault. Hunting such an animal would have required immense courage, skill, and strategic planning.
While early North Americans are well-known for hunting mammoths and other large game, the idea that they systematically hunted giant sloths had previously been a matter of speculation. This discovery provides the first conclusive surface evidence of such interactions in the Americas, confirming that these imposing animals were indeed on the menu for human hunters. The challenge they posed likely necessitated the development of specific hunting techniques to overcome their size and defensive capabilities.
Coordinated Hunting Strategies
The trackways at White Sands do not just tell the story of a single hunter. In addition to the footprints found following directly behind the sloth, researchers identified other sets of human tracks at a safe distance from the main confrontation. This suggests a group effort, a classic hunting strategy involving distraction and teamwork. One or more hunters may have been tasked with stalking the animal directly, keeping its attention focused forward, while others moved in from the sides or rear to attempt a killing blow.
This method of using misdirection would have been crucial for minimizing risk when facing the sloth’s dangerous claws. The scene reconstructed by the scientists suggests a calculated and organized hunt, not a desperate or opportunistic encounter. The hunters were “practiced at it,” the researchers concluded, indicating this was likely a common and well-rehearsed activity for these early people. It demonstrates a sophisticated understanding of animal behavior and the ability to execute complex, cooperative plans.
Context of a Lost World
The discovery raises broader questions about the extinction of North America’s megafauna. Giant ground sloths, along with mammoths, saber-toothed cats, and other large animals, vanished around the end of the last Ice Age, roughly 10,000 years ago. The disappearance of these giants has long been debated by scientists, with leading theories pointing to a combination of rapid climate change and human hunting pressure.
While the White Sands footprints do not resolve this debate, they add a crucial piece of evidence. The tracks confirm that humans were not just scavengers but were actively and effectively hunting these giant creatures. This new understanding of the predator-prey relationship between humans and sloths strengthens the argument that human hunting played a significant role in the eventual decline of these species. The footprints end without revealing the final outcome of this particular hunt, leaving it unclear who was victorious that day. However, the very existence of the tracks provides an undeniable record of the conflict that defined the end of an epoch.
