People probably settled in America much earlier than previously thought. This is confirmed by new analyzes of finds in the US state of New Mexico. In 2021, a research team there dated human footprints to be more than 20,000 years old. According to this, the first humans would not have set foot on the continent around 16,000 years ago, when the glaciers had retreated after the peak of the last ice age, but thousands of years earlier, the team wrote in the scientific journal at the time Science.
Although independent experts attested to the group’s careful work, in view of the spectacular results, they called for the age to be confirmed using other dating methods. This is now presented by a group led by Jeffrey Pigati from the US Geological Survey, who was also involved in the study at the time. also in Science.
It is considered certain that man reached America from Siberia. But the question of when is controversial. About 20,000 years ago, when the glaciers were at their greatest extent during the last ice age, an ice sheet blocked the way to North America. That’s why experts currently assume that the continent was only populated much later. But according to the footprints, people must have been in America at the peak of the cold period.
In White Sands National Park in southern New Mexico, researchers discovered eight groups with a total of around 60 footprints. The Tularosa Basin there, now a gypsum field covered by dunes, was then covered by lakes whose sediments preserved the footprints.
It is therefore unclear when people first set foot on the American continent
The prints clearly come from modern humans, most of them teenagers and children. The layers were dated using the radiocarbon method based on the abundance of aquatic plant seeds present in them Ruppia cirrhosa.
With the new study, the team responds to criticism that the seeds may have originally come from older layers of soil. Now the group, which also included the lead author at the time, Matthew Bennett from Bournemouth University in southern England, also used the radiocarbon method to date the age of the prints using conifer pollen from the same layer. The team also determined the age using so-called optically stimulated luminescence dating of quartz grains. This method measures when a layer of earth was last exposed to sunlight.
Radiocarbon dating of three different pollen samples revealed an age of around 23,000 years, and according to the luminescence method, the prints are at least 21,500 years old. This means that three different methods have now independently resulted in a similar time horizon, emphasizes the group. This supports the conclusion that people were already living in America at the height of the last Ice Age.
In one Science-Bente Philippsen writes a comment from the National Laboratory for Age Determination at the Norwegian University of Science and Technology in Trondheim, radiocarbon dating is common, but there are various possible sources of error, for example if the seeds moved from one layer of the earth to another or if they had absorbed older carbon through groundwater. Luminescence dating could also be subject to errors. However, it is “highly unlikely that different methods with different materials always lead to systematic errors in the same direction and of the same magnitude,” she writes. Therefore, the overall data strongly suggested that people were actually already living in America at the height of the last Ice Age. It is unclear when humans first set foot on the continent.