In the heart of New Mexico’s White Sands National Park, scientists have embarked on a captivating journey to confirm the age of human footprints, unveiling a fascinating chapter in America’s prehistory. These enigmatic footprints, dating back approximately 23,000 years, have become the subject of rigorous scrutiny, employing various dating techniques and igniting debates among archaeologists. In this article, we delve into the intriguing world of ancient footprints and the quest to validate their ages.
Unveiling America’s Ancient Footprints
The footprints at White Sands National Park are believed to be between 23,000 to 21,000 years old. A recent study suggests that these footprints are the oldest known fossilized imprints left by humans in North America, challenging our understanding of early human migration on the continent. However, not everyone in the scientific community agrees with these findings.
To ascertain the age of these footprints, researchers employed two dating techniques, a response to criticisms aimed at a previous study from 2021, which questioned the reliability of the materials used for dating. Now, all three sets of results, including the previously disputed ones and two new findings from different dating methods, converge to indicate that the footprints indeed date back to 23,000 to 21,000 years ago.
This revelation firmly places the footprints within the frigid depths of the Last Glacial Maximum period, approximately 26,500 to 19,000 years ago.
The historical significance of these footprints cannot be overstated. Previously, archaeologists believed that the Clovis people, known for their distinctive spearheads, were the first humans to arrive in America around 13,000 years ago. However, recent decades have witnessed the discovery of solid evidence for pre-Clovis periods and humans residing in America more than 13,000 years ago. Nevertheless, many of these newly discovered sites had weak or only slightly older evidence than the Clovis culture.
The White Sands footprints now stand as the oldest direct human evidence in North America, significantly pushing back the timeline of the first Americans’ arrival.
Jeffrey Pigati, who co-led the study with Kathleen Springer, explains, “When the first article came out, many archaeologists reached out to us, saying, ‘This was just a matter of time.’ We knew people had been here before. Now we have very strong evidence of humans being here during the Last Glacial Maximum.”
However, in 2022, a group of archaeologists raised concerns about the reliability of the materials dated in the initial article, particularly the seeds of the water plant Ruppia cirrhosa.
Scientists had discovered organic remnants suitable for radiocarbon dating within the footprints, and one of the critical critics, Loren Davis, an anthropology professor at Oregon State University, argued, “Ruppia is a notorious poor indicator of its age.”
Davis pointed out that unlike other organisms that breathe in carbon-14 from the atmosphere, Ruppia takes its carbon from the lake water. If ancient carbon mixes into the groundwater, younger plants may yield older dates.
Davis and his colleagues suggested that the White Sands team should utilize Optically Stimulated Luminescence (OSL) dating, a technique that estimates the time since quartz or feldspar grains were last exposed to intense heat or sunlight, providing a different perspective on the footprints’ age.
In a recently published article in Science, researchers followed this recommendation.
The team examined the quartz grains beneath the footprints using optically stimulated luminescence dating, concluding that the minimum age of the layers containing the footprints is approximately 21,500 years.
Additionally, the researchers isolated three soil samples from the same layers as the Ruppia seeds, each containing 75,000 pine pollen grains. They then conducted radiocarbon dating on these samples. Pine trees obtain their carbon-14 from the atmosphere, eliminating the potential issues associated with Ruppia. The dates obtained, around 23,000 years ago, align with both the seed and quartz grain ages.
Pigati confidently states, “If seed dates, pollen dates, and luminescence dates all match, then the case is closed. We can stop debating about the dates.”
However, Davis remains skeptical, asserting, “Not yet.”
Referring to a map showing where the White Sands team collected OSL samples, Davis explains, “It is clear that all three OSL dates come from sediments stratigraphically below the footprints.”
Therefore, it remains possible that, as one OSL sample suggests, the quartz grains settled long before the footprints, perhaps between 19,800 and 16,200 years ago.
Davis emphasizes the importance of researchers continuing their efforts to obtain OSL dates from sediments that encapsulate the footprints. The shifting of pollen samples between layers over time could mean that they are older than the footprints themselves.
Thomas Higham, an archaeologist and radiocarbon dating expert from the University of Vienna, who was not part of the study, praises the research, stating, “I think this is a significant contribution, a very convincing and detailed study.”
The age of America’s oldest human footprints at White Sands National Park continues to be a subject of scientific inquiry and debate. While recent studies have provided compelling evidence supporting their ancient origin, the discussion is far from settled. This ongoing exploration into the distant past promises to reshape our understanding of early human migration in North America.