Ancient Footprints: Confirming Human Presence in New Mexico 21,500 Years Ago
06.10.2023 posted by Admin
New research has recently affirmed that human footprints in what is now the New Mexico desert are no older than 21,500 years, settling a controversial discovery made in 2021.
Back then, the revelation of these ancient imprints in White Sands, New Mexico left many astonished but also somewhat skeptical. However, a team, which includes some of the same scientists, has now conducted more rigorous dating methods to confirm the previously disputed finding.
This new evidence strengthens the likelihood that humans indeed inhabited what is currently North America during the Last Glacial Maximum period.
Geologist Jeff Pigati from the US Geological Survey (USGS), who co-led this latest research effort, explains that some members of the archaeological community initially doubted the accuracy of their dating methods to make such an extraordinary claim. However, their meticulous approach in this current study has paid off.
The initial dating relied on radiocarbon dating of seeds from an aquatic plant called Ruppia cirrhosa, also known as spiral ditchgrass, found within the fossilized footprints. Radiocarbon dating is based on the radioactive isotope C-14, formed in Earth's atmosphere as cosmic rays interact with nitrogen. C-14 gets absorbed by plants and animals during their lifetime.
Since C-14 decays into stable carbon at a known rate, scientists can analyze the C-14 to stable carbon ratios in a sample to determine its age.
The aquatic nature of the plant used for the original dating raised questions, as water can store carbon, potentially making the plant material seem much older than it actually is. Even when their initial findings were published, the researchers continued to explore other dating methods to ensure the accuracy of their results.
Geologist Kathleen Springer of the USGS, who co-led the research, emphasizes the importance of independent chronological verification. To achieve this, the team collected conifer pollen from the same geological layer as the ditchgrass seeds, suggesting they were deposited simultaneously. Conifers are terrestrial plants, which means that any carbon within them would have come from the atmosphere, eliminating the potential for the same carbon reservoir error as in aquatic plants.
The team conducted radiocarbon dating on approximately 75,000 pollen grains from three separate samples and also employed a different dating technique on quartz found in the layers with the footprints. This technique, called optically stimulated luminescence, determines the last time a mineral sample was exposed to sunlight.
Both sets of results corroborated their earlier findings, with the conifer pollen dating to between 22,600 and 23,400 years ago and the quartz last seeing sunlight around 21,500 years ago.
When combined with the ditchgrass data, these multiple lines of evidence all point to the same conclusion: humans were indeed present in North America during the Last Glacial Maximum. This discovery holds great significance in unraveling the history of human migration and habitation on our ever-changing planet.
Back then, the revelation of these ancient imprints in White Sands, New Mexico left many astonished but also somewhat skeptical. However, a team, which includes some of the same scientists, has now conducted more rigorous dating methods to confirm the previously disputed finding.
This new evidence strengthens the likelihood that humans indeed inhabited what is currently North America during the Last Glacial Maximum period.
Geologist Jeff Pigati from the US Geological Survey (USGS), who co-led this latest research effort, explains that some members of the archaeological community initially doubted the accuracy of their dating methods to make such an extraordinary claim. However, their meticulous approach in this current study has paid off.
The initial dating relied on radiocarbon dating of seeds from an aquatic plant called Ruppia cirrhosa, also known as spiral ditchgrass, found within the fossilized footprints. Radiocarbon dating is based on the radioactive isotope C-14, formed in Earth's atmosphere as cosmic rays interact with nitrogen. C-14 gets absorbed by plants and animals during their lifetime.
Since C-14 decays into stable carbon at a known rate, scientists can analyze the C-14 to stable carbon ratios in a sample to determine its age.
The aquatic nature of the plant used for the original dating raised questions, as water can store carbon, potentially making the plant material seem much older than it actually is. Even when their initial findings were published, the researchers continued to explore other dating methods to ensure the accuracy of their results.
Geologist Kathleen Springer of the USGS, who co-led the research, emphasizes the importance of independent chronological verification. To achieve this, the team collected conifer pollen from the same geological layer as the ditchgrass seeds, suggesting they were deposited simultaneously. Conifers are terrestrial plants, which means that any carbon within them would have come from the atmosphere, eliminating the potential for the same carbon reservoir error as in aquatic plants.
The team conducted radiocarbon dating on approximately 75,000 pollen grains from three separate samples and also employed a different dating technique on quartz found in the layers with the footprints. This technique, called optically stimulated luminescence, determines the last time a mineral sample was exposed to sunlight.
Both sets of results corroborated their earlier findings, with the conifer pollen dating to between 22,600 and 23,400 years ago and the quartz last seeing sunlight around 21,500 years ago.
When combined with the ditchgrass data, these multiple lines of evidence all point to the same conclusion: humans were indeed present in North America during the Last Glacial Maximum. This discovery holds great significance in unraveling the history of human migration and habitation on our ever-changing planet.