When the discovery of fossilized footprints in what is now New Mexico was announced in 2021, it was a bombshell moment for archeology that seemingly rewrote a chapter in the human story. Now new research offers further evidence of their importance. Although they look like they could have been made yesterday, the tracks were pressed into the mud between 21,000 and 23,000 years ago, according to radiocarbon dating of the seeds of an aquatic plant that were preserved above and below the fossils.In the video player above: See images of the tracks from the service National Park Service This date dramatically shifted the timeline of human history in the Americas, the last landmass to be inhabited by prehistoric humans. The 61 dated footprints, which were discovered in the Tularosa Basin, near the edge of an ancient lake in White Sands National Park, were taken at a time when many scientists think massive ice sheets closed off human passage to North America, suggesting that humans arrived in region even earlier. However, some archaeologists have questioned the age of the prints identified by these initial finds. Skeptics have noted that aquatic plants such as Ruppia cirrhosa – the one used in the 2021 study – may obtain carbon from dissolved atoms in the water rather than the air, which may lead to a misleadingly early date. In a follow-up study published Thursday in the journal Science, the researchers said they generated two new lines of evidence to support their original data. research geologist at the US Geological Survey and co-author of the new science paper in the press release.Video below: More on the study that shows humans reached the Americas 7,000 years earlier than thought“We were also certain of our original age as strong geological , hydrologic and stratigraphic evidence, but we knew independent chronological control was critical.” When and how early humans first migrated to the Americas has long been debated and remains poorly understood. Current estimates of the number of first inhabitants range from 13,000 years ago to more than 20,000 years ago. However, the earliest archaeological evidence of settlement in the region is sparse and often controversial, making the tracks particularly important. Confirming the Age of the Ancient Traces In their follow-up study, the researchers focused on radiocarbon dating the conifer pollen because it comes from terrestrial According to a press release, the researchers were able to isolate about 75,000 pollen grains collected from exactly the same layers as the original seeds. Thousands of grains are required to achieve the mass necessary for one radiocarbon measurement. The age of the pollen corresponded to the age of the seeds. The team also used a dating technique known as optically stimulated luminescence, which determines when the quartz grains in the fossil sediment were last exposed to sunlight. This method indicated that the quartz had a minimum age of 21,500 years.” The immediate reaction in some quarters of the archaeological community was that the precision of our dating was insufficient to make the extraordinary claim that humans were present in North America during the last glacial period. The maximum, ” said Jeff Pigati, a USGS geologist and co-author of the study. “But our targeted methodology in this current research really paid off.” This study helps shed light on the big story of human evolution, but much remains unknown about how the Americas were settled. It’s unclear whether the first humans arrived by ship or came over a land bridge from Asia. Even with advances in genetic evidence, it remains unclear whether one or many populations of early modern humans made the long journey. Bente Philippsen, associate professor and expert in radiocarbon dating at the Norwegian University of Science and Technology , said determining the age of pollen grains is “a complex process that comes with the risk of contamination.” What’s more, she noted in a commentary published alongside the study, the data derived from luminescence have large measurement uncertainties. However, she said the new study’s findings overall “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, extending as far south as New York. Cincinnati and Des Moines.” , Iowa. Ice and cold temperatures would have made travel between Asia and Alaska impossible during that time, meaning the people who made the tracks likely arrived much earlier. Jennifer Raff, associate professor at the University of Kansas and author of In “Origin: Genetic History of the Americas,” she said the trace findings were a “big deal” for the area. “The Americas were the last step in the global journey of modern humans around the world,” she said by email. “It’s fascinating to imagine what it must have been like to enter a new region and grapple with the challenges (and opportunities) the new environment would present.”
When the discovery of fossilized footprints in what is now New Mexico was announced in 2021, it was a bombshell moment for archeology that seemingly rewrote a chapter in the human story. Now new research offers further evidence of their importance.
While they look like they could have been made yesterday, the footprints were pressed into the mud between 21,000 and 23,000 years ago, according to radiocarbon dating of the seeds of an aquatic plant preserved above and below the fossils.
In the video player above: See pictures of the tracks from the National Park Service
This date dramatically shifted the timeline of human history in the Americas, the last landmass to be settled by prehistoric humans. The 61 dated footprints, which were discovered in the Tularosa Basin, near the edge of an ancient lake in White Sands National Park, were taken at a time when many scientists think massive ice sheets closed off human passage to North America, suggesting that humans arrived in region even earlier.
However, some archaeologists have questioned the age of the tracks established by these initial finds. Skeptics noted that aquatic plants such as Ruppia cirrhosa – the one used in the 2021 study – may obtain carbon from dissolved atoms in the water rather than the air, which could lead to a misleadingly early date.
in follow-up studies published Thursday in the journal Science, the researchers said they generated two new lines of evidence to support their original data.
“Even after the original work was published, we went ahead to test our results with multiple lines of evidence,” said Kathleen Springer, a research geologist with the US Geological Survey and co-author of the new science paper. release.
Video below: More on study that shows humans reached America 7,000 years earlier than thought
“We were confident of our original age, as well as the strong geological, hydrological and stratigraphic evidence, but we knew that independent chronological verification was critical.”
When and how early humans first migrated to the Americas has long been debated and remains poorly understood. Current estimates of the number of first inhabitants range from 13,000 years ago to more than 20,000 years ago. However, the earliest archaeological evidence of settlement in the region is sparse and often controversial, making the tracks particularly important.
Confirming the age of ancient traces
In their follow-up study, the researchers focused on radiocarbon dating conifer pollen because it comes from a terrestrial plant and avoids the problems that can arise when dating aquatic plants like Ruppia, according to the press release.
The researchers were able to isolate about 75,000 pollen grains from each sample collected from exactly the same layers as the original seeds. Thousands of grains are required to achieve the mass necessary for one radiocarbon measurement. The age of the pollen corresponded to the age of the seeds.
The team also used a dating technique known as optically stimulated luminescence, which determines when the quartz grains in the fossil sediment were last exposed to sunlight. This method indicated that the quartz had a minimum age of 21,500 years.
“The immediate reaction in some quarters of the archaeological community was that the precision of our dating was insufficient to make the extraordinary claim that humans were present in North America during The Last Glacial Maximum,” said Jeff Pigati, a USGS geologist and co-author of the study. “But our targeted methodology in this current research really paid off.”
This study helps shed light on the big story of human evolution, but there is still much that is unknown about how the Americas were settled.
It is unclear whether the first humans arrived by boat or came over a land bridge from Asia. Even with advances in genetic evidence, it is unclear whether one or many populations of early modern humans made the long journey.
Bente Philippsen, an associate professor and expert in radiocarbon dating at the Norwegian University of Science and Technology, said determining the age of a pollen grain is “a complex process that comes with the risk of contamination”.
What’s more, she noted in a commentary published alongside the study, the luminescence-derived data have large measurement uncertainties.
But she said the new study’s findings overall “strongly suggest” a human presence in the Americas around the time of the Last Glacial Maximum, the period between 19,000 and 26,000 years ago when two massive ice sheets covered the northern third of North America. extending as far south as New York, Cincinnati and Des Moines, Iowa.
Ice and cold temperatures would have made travel between Asia and Alaska impossible during that time, meaning the people who made the tracks probably arrived much earlier.
Jennifer Raff, an associate professor at the University of Kansas and author of “Origin: A Genetic History of the Americas,” said finding the traces is a “big deal” for the area.
“The Americas were the last step in the global journey of modern humans around the world,” she said by email. “It’s fascinating to imagine what it must have been like to enter a new region and grapple with the challenges (and opportunities) the new environment would present.”