When it was announced that fossilized footprints had been discovered in what is now New Mexico in 2021, it was a shocking moment for archaeology that seemed to rewrite a chapter in humanity’s story. Now new research provides further evidence of their importance. While they look like they were formed yesterday, the footprints were pressed into the clay 21,000 to 23,000 years ago, according to radiocarbon dating of an aquatic plant seed preserved above. Below the excavations. In the video player above: See images of the footprints from the National Park Service This date dramatically pushed the timeline of human history in the Americas, the last land mass inhabited by prehistoric people. The 61 dated prints, which were discovered in the Tularosa Basin, near the edge of an ancient lake in White Sands National Park, were made at a time when many scientists believe massive ice sheets had closed off human passage to North America, suggesting that Humans had arrived in the area much earlier. However, some archaeologists have questioned the age of the footprints identified by those initial findings. Skeptics have pointed out that aquatic plants like Rubia cirrhus — the one used in the 2021 study — could obtain carbon from atoms dissolved in water rather than air, which could lead to a misleading early date. In a follow-up study published Thursday in the journal Science, researchers said they have produced two new lines of evidence to support the preliminary dates. “Even when the original work was published, we were moving forward to test our findings using multiple lines of evidence,” Kathleen Springer said. A USGS research geologist and co-author of the new Science paper, said in a press release. Video below: More about the study showing that humans arrived in the Americas 7,000 years earlier than thought “We were also confident in our origins as strong geological, hydrological, and stratigraphic evidence, but we knew that independent temporal control was crucial. Current estimates of early populations range from 13,000 years ago to more than 20,000 years ago. However, older archaeological evidence for settlement of the area is sparse and often controversial, which makes the footprints of particular interest. It avoids problems that can arise when dating aquatic plants like Rubia, according to the press release The scientists were able to isolate about 75,000 pollen grains, collected from the same layers as the original seeds, for each sample. Thousands of grains are needed to achieve the mass needed for a single radiocarbon measurement. The age of the pollen grains matches the age of the seeds. The team also used a technique Dating known as optically stimulated luminescence, which determines the last time quartz grains in fossil sediments were exposed to sunlight. This method puts the minimum age of quartz at 21,500 years. “The limit is 21,500 years old,” said Jeff Bigatti, a USGS geologist and co-lead author of the study. Al-Aqsa. “But our targeted methodology in this current research has really paid off.” This study helps shed light on the larger story of human evolution, but there is still much that remains unknown about how the Americas were populated. Across a land bridge from Asia. Despite advances in genetic evidence, it is not clear whether one or more groups of early modern humans made such a long journey. Determining the age of cereal pollen is “a complex process that comes with the risk of contamination,” said Bente Philipsen, an associate professor and radiocarbon dating expert at the Norwegian University of Science and Technology. What’s more, she noted in a commentary published alongside the study, that dates derived from scintillation have significant measurement uncertainties. However, she said that overall, the new study’s findings “strongly suggest” a human presence in the Americas around the time of the Last Glacial Maximum, a period between 19,000 and 26,000 years ago when two massive ice sheets covered the northern third of North America, reaching… South as far as New York City, Cincinnati and Des Moines, Iowa. Ice and cold temperatures would have made the journey between Asia and Alaska impossible during that period, meaning that the people who made the footprints likely arrived much earlier. Jennifer Ruff, an associate professor at the University of Kansas and author of “Descent” and “The Genetic History of the Americas,” said via email that the fingerprinting results were a “big deal” for the field. “The American continents were the final step in the global journey of modern humans across the globe,” she added via email. “It’s amazing to imagine what it would be like to enter a new area and face the challenges (and opportunities) that the new environments would present.”
When it was announced that fossilized footprints had been discovered in what is now New Mexico in 2021, it was a shocking moment for archaeology that seemed to rewrite a chapter in humanity’s story. Now new research provides additional evidence of its importance.
While they look like they were formed yesterday, the footprints were pressed into the clay 21,000 to 23,000 years ago, according to radiocarbon dating of aquatic plant seeds preserved above and below the fossils.
In the video player above: See photos of the footprints from the National Park Service
This date pushed back the timeline of human history significantly into the Americas, the last land mass settled by prehistoric peoples. The 61 dated prints, which were discovered in the Tularosa Basin, near the edge of an ancient lake in White Sands National Park, were made at a time when many scientists believe massive ice sheets had closed off human passage to North America, suggesting that Humans arrived in the area even earlier.
However, some archaeologists have questioned the age of the footprints identified by those initial findings. Skeptics have pointed out that aquatic plants like Rubia cirrhus — the one used in the 2021 study — could obtain carbon from atoms dissolved in water rather than air, which could lead to a misleading early date.
in Follow-up study Published Thursday in the journal Science, the researchers said they have produced two new lines of evidence to support their initial dates.
“Even while publishing the original work, we were moving forward to test our findings using multiple lines of evidence,” Kathleen Springer, a research geologist at the USGS and co-lead author of the new paper, said in a journal article. launch.
Video below: More about the study showing that humans arrived in the Americas 7,000 years earlier than thought
“We were confident in our original ages, as well as the strong geological, hydrological and stratigraphic evidence, but we knew that independent temporal control was critical.”
When and how early humans migrated to the Americas has long been debated and remains poorly understood. Current estimates of the first inhabitants range from 13,000 years ago to more than 20,000 years ago. However, early archaeological evidence of settlement in the area is sparse and often controversial, making the footprints of particular interest.
Confirming the age of ancient footprints
In their follow-up study, the researchers focused on radiocarbon dating of conifer pollen, because it comes from a terrestrial plant and avoids problems that can arise when dating aquatic plants like Rubia, according to the press release.
Scientists were able to isolate about 75,000 pollen grains, collected from the same layers as the original seeds, for each sample. Thousands of grains are needed to achieve the mass needed for a single radiocarbon measurement. The age of the pollen is identical to the age of the seeds.
The team also used a dating technique known as optically stimulated luminescence, which determines the last time quartz grains in fossil sediments were exposed to sunlight. This method indicates that the quartz is at least 21,500 years old.
“The immediate reaction in some circles of the archaeological community was that the accuracy of our dating was insufficient to make an exceptional claim that humans were present in North America during the Paleolithic.” Last glacial maximumsaid Jeff Bigatti, a USGS geologist and co-lead author of the study. “But our targeted methodology in this current research has really paid off.”
This study helps shed light on the larger story of human evolution, but there is still much that remains unknown about how the Americas were populated.
It is not clear whether the first humans arrived by boat or came via a land bridge from Asia. Despite advances in genetic evidence, it is not clear whether one or more groups of early modern humans made the long journey.
Determining the age of pollen is “a complex process that comes with the risk of contamination,” said Bente Philipsen, an associate professor and radiocarbon dating expert at the Norwegian University of Science and Technology.
Furthermore, she noted in a commentary published alongside the study, the scintillation-derived dates have significant measurement uncertainty.
However, she said overall the new study’s results “strongly suggest” a human presence in the Americas around the time of the Last Glacial Maximum, a period between 19,000 and 26,000 years ago when two massive ice sheets covered the northern third of North America. It reaches as far south as New York City, Cincinnati and Des Moines, Iowa.
Ice and cold temperatures would have made travel between Asia and Alaska impossible during that period, meaning that the people who left the footprints would likely have arrived much earlier.
The fingerprinting findings were a “big deal” for the field, said Jennifer Ruff, an assistant professor at the University of Kansas and author of “Descent: The Genetic History of the Americas.”
“The American continents were the final step in the global journey of modern humans across the globe,” she said via email. “It’s amazing to imagine what it would be like to enter a new area and face the challenges (and opportunities) that the new environments would present.”
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