Our species, Homo sapiens, emerged in Africa between 150,000 and 250,000 years ago. Then, around 80,000 years ago, the first modern humans left the black continent and spread to the rest of the world. But they didn't get everywhere at once. On an ancient route, our direct ancestors first occupied Asia, where remains that are more than 70,000 years old have been found. Then it was the turn of Europe, where they did not enter until around 45,000 ago, and finally America, the last continent to be occupied, around 14,000 ago. Or at least that's what was believed. In recent years, in fact, different dating of American human remains are yielding much earlier dates, even more than 10,000 years older, for the first human occupations of the continent. Something that challenges the dominant theory, according to which the last ice age, which began 110,000 years ago and ended 12,000 years ago, left the American continent isolated, closing the Bering Strait for tens of thousands of years, the only land passage that allows access to America from Siberia, at the eastern end of Asia. For supporters of this idea, therefore, it was absolutely impossible to reach America on foot before the ice retreated. An idea, on the other hand, that the scarcity of ancient archaeological evidence seemed to reinforce. Thus, on September 23, 2021, unexpected news shook the international archaeological community and raised serious doubts about some of its most used methods. That day, in fact, an international team of researchers published an article in 'Science' in which it was stated that a series of human footprints found in various strata of the bed of an ancient lake in White Sands National Park, in New Mexico , showed that the area was occupied for at least two millennia, between 23,000 and 21,000 years ago. That is, these footprints were almost 10,000 years older than they should be and, to make matters worse, they suggested a long and stable human occupation of the area precisely at the height of the Last Glacial Maximum. "The immediate reaction in some circles of the archaeological community," explains Jeff Pigati, one of the authors of that study, "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. Since the publication of that study, the accuracy of the radiocarbon dates has been debated, arguing that the ancient seeds of the aquatic plant (Ruppia cirrhosa) that were used to date the surfaces in which the footprints were embedded have the potential to be affected. due to the effects of ancient carbon reservoirs that could influence the ages obtained and make them appear older than they really are. New study, new evidence But now, Pigati and his colleagues have reconfirmed their results. And in a new study that appears today in 'Science' and of which he is co-lead author, the same team has used new radiocarbon and luminescence dating techniques, confirming the controversial antiquity of the White Sands footprints. Directly addressing widespread criticism of their previous work, the researchers explain that the ages, obtained this time independently from multiple sources, show "conclusively" that the footprints were left over a period spanning 23,000 years ago. 21,000 years ago, proving that humans were present in the southern region of North America at a time when it was thought impossible. "Our methodology in this new research - says Pigati - has borne fruit." In their new work, Pigati and his colleagues analyzed the age of terrestrial pollen grains collected from the same strata as the Ruppia seeds used in 2021. Unlike seeds, pollen from conifers fixes atmospheric carbon and therefore Therefore, it is not subject to possible effects of ancient carbon pools. Dates are confirmed The results show that the calibrated ages resulting from radiocarbon analysis range between 23.4 ± 2.5 and 22.6 ± 2.3 thousand years ago. In addition, the authors also obtained optically simulated luminescence ages of the sediments within the strata containing the footprints, which produced a minimum age of 21.5 ± 1.9 thousand years ago. In both cases, the researchers obtained dates practically the same as those reported in the 2021 study. MORE INFORMATION news No The cold could not overcome them: they lived in the Iberian mountains, even in the middle of glaciation news Yes Anne L'Huillier, Nobel Prize in Physics 2023: "We have problems, like climate change, more important than reaching the Moon" "Even as the original work was published - explains Kathleen Springer, also co-lead author of the new study - we were moving forward to test our results with multiple lines of evidence and independent chronological techniques. While we were confident in the ages of the original seeds, we also wanted to build community trust in them. "Our new ages, combined with the strong geological, hydrological and stratigraphic evidence, unequivocally support the conclusion that humans were already present in North America during the last Glacial Maximum."