2023-10-05 20:00:04
A team of researchers from the United States and Europe has used radiocarbono (or carbon-14) and luminescence optically simulated to confirm that fossilized human footprints from the White Sands National Park (New Mexico, USA) are between 20,000 and 23,000 years old. The results are published in the latest issue of Science.
The authors have already published a previous study in 2021 on the dating of these footprints in this same magazine with similar results (between 21,000 and 23,000 years old), which received multiple criticisms from the scientific community.
Now, in response to the controversy generated, the team, in which researchers from the United States Geological Survey (USGS) have participated, claims to have evidence, confirmed with several independent dating lineswhich point to the same approximate age.
This demonstrates, according to the authors, “that humans were present in southern North America during the Last Glacial Maximum” (LGM, for its acronym in English). It was previously thought that they had arrived in that area between 13,500 and 16,000 years ago.
Fossilized human footprints formed in soft mud on the margins of a shallow lake now part of White Sands National Park
Fossilized human footprints were formed in soft mud on the margins of a shallow lake which is now part of Alkali Flata large area of dunes in White Sands. David Bustosadministrator of the national park’s resources program, was the first to discover these footprints in 2009. Bustos, along with Matthew Bennetta geologist at Bournemouth University (United Kingdom) and other USGS scientists began studying the site in more detail in 2019.
As explained to SINC Kathleen Springera USGS research geologist and co-author of the work, “the initial radiocarbon results from the 2021 work were controversial because the seeds of the aquatic plant (Ruppia cirrhosa) that we use to date the surfaces on which the footprints were marked, have the potential to suffer carbon deposition effects that could compromise the accuracy of their dating.
Conifer pollen analysis
But now, “in the new study we have focused on conifer pollen because these species – mainly pines – are terrestrial plants and they are not affected by deposition effects, since their carbon comes directly from the atmosphere through photosynthesis,” he adds.
Springer acknowledges that “the drawback of pollen dating is that it is tiny, but the methods we used in this research allowed us to isolate 75,000 pure pollen grains per sample, which was enough to obtain solid radiocarbon dates.”
The methods we used allowed us to isolate 75,000 pure pollen grains per sample, which was enough to obtain solid radiocarbon dates.
Kathleen Springer, USGS Research Geologist
Additionally, “luminescence dating of quartz grains isolated from sediments was used, providing completely independent verification of the radiocarbon dates,” he notes.
“Even as we published the previous study, we had already started testing our results with multiple lines of evidence. We were confident in our original dating, as well as in the solid geological, hydrological and stratigraphic evidence, but we knew that independent chronological control was essential,” Springer emphasizes.
Illustration of the site studied during the Last Glacial Maximum showing the coexistence of humans and megafauna over time. / Karen Carr / National Park Service
The scientist emphasizes that the conclusions obtained through “radiocarbon dating of the pollen and luminescence of the sediments show that the chronological framework originally established for the footprints in the national park is solid.”
Radiocarbon dating of pollen and luminescence dating of sediments show that the chronological framework originally established for the national park’s human footprints is solid
Kathleen Springer
“Case closed and controversy resolved”
For Springer, the new study of the fossilized footprints from White Sands closes the case and resolves the controversy: “Combined with the geological, hydrological, stratigraphic, chronological and climatic evidencepreviously reported, the congruence of calibrated carbon-14 dating of aquatic Ruppia seeds, those of terrestrial pollen grains, and those achieved by luminescence supports the conclusion that humans were present in North America during the Last Glacial Maximum.
What does this confirmation mean? According to the geologist, “humans were in southern North America during the LGM, between 21,000 and 23,000 years ago, and this means that They were there before the huge ice sheets closed”.
“Our findings – he concludes – extend the known range of human occupation in the area by thousands of years, which has iImplications for migratory routes, ancient DNA studies and linguistics”.
The story behind footprints engraved in the mud
As it appears in the information on the website of the White Sands National ParkFor about 80 years, only a small collection of fossilized footprints was known to exist, but in 2006, a group of scientists observed dark spots on the lake bed that appeared to be footprints. Their curiosity led them to unearth these dark spots in 2009, which ended up revealing human footprints and a year later those of a direwolf. These foot marks were next to ancient seedswhich scientists then dated to more than 18,000 years ago.
In 2018, researchers discovered what they believe are the footsteps of a woman. These tell a story that may still seem familiar. Her footprints show her walking for almost a mile, with the footprints of a small child occasionally appearing next to hers. The evidence suggests that he carried the child in his arms, changing him from side to side and putting him down from time to time While walking. The footprints widened and slipped in the mud due to the extra weight he was carrying.
Based on height and walking speed, it appears that most of the marks found come from teenagers and children. According to him 2021 study in Science“a hypothesis is the division of labourin which adults are dedicated to specialized tasks, while fetching and carrying is delegated to adolescents accompanied by children, who together leave a greater number of footprints, a pattern that is common to all excavated surfaces.
In a scene from the Ice Age, a woman with a child in her arms on the shores of ancient Lake Otero leaves footprints in the mud. / Karen Carr
Reference:
Jeffrey S. Pigati, Kathleen B. Springer, Matthew R. Bennett et al. “Independent age estimates resolve the controversy of ancient human footprints at White Sands”. Science (October, 2023)
Rights: Creative Commons.
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