New test confirms the age of ancient human footprints in New Mexico

A new study uses two additional dating approaches to confirm the age of fossilized footprints in New Mexico’s White Sands National Park, showing that humans lived thousands of years earlier than previously thought. He was exploring the terrain of North America.

Researchers announced Thursday that the footprints are about 21,000 to 23,000 years old, based on radiocarbon and light-stimulated luminescence dating methods, suggesting that our species homo sapiens It had already established a foothold in North America during the most extreme conditions of the last ice age.

In the midst of vast glaciers, huge ice sheets covered large swathes of the continent, reaching as far south as Illinois.

A 2021 study by these researchers also dated the footprints to about 21,000 to 23,000 years ago, based on small plant seeds embedded in the sediment next to them. found. This was met with skepticism from some scientists who questioned the dating’s conclusions.

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“While each dating method has advantages and disadvantages, when all three different methods converge on the same age range, the resulting age is very robust,” says a study from the United States Geological Survey (USGS). said geologist Jeff Pigati. -lead author of the study It was published in the magazine science.

“Our initial results were controversial, and we knew from the beginning that we needed to independently assess seed age to build community trust. This paper supports that. ,” added Kathleen Springer, study co-lead author and USGS research geologist. In Denver.

Homo sapiens originated in Africa more than 300,000 years ago and has since spread throughout the world. Scientists believe that our species entered North America from Asia across a land bridge that once connected Siberia and Alaska.

Previous archaeological evidence suggested that human occupation of North America began around 16,000 years ago, said study co-author Matthew Bennett, professor of environmental and geographic science at Bournemouth University in the UK. That’s what it means.

“Indigenous peoples were there earlier than thought, before a great ice barrier at the height of the last Ice Age peak closed the path south from Alaska. “We still don’t know how they got there. White Sands is just one stop. “For now, it’s a map,” Bennett said.

A 2021 study dated the fossilized footprints using radiocarbon dating to determine the age of seeds of a common aquatic plant called spiral ditch grass found with the fossilized footprints.

This technique is used to determine the age of organic material as old as approximately 60,000 years, based on the decay of an isotope called carbon-14, a type of carbon element. Living organisms absorb carbon-14 into their tissues. When an organism dies, this isotope transforms into other atoms over time and serves as an indicator for determining age.

The fact that aquatic plants can acquire carbon from dissolved carbon atoms in water could throw off age estimates and sparked controversy over the 2021 conclusion.

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This time, the researchers used radiocarbon dating on conifer pollen, circumventing concerns about aquatic plants. They isolated thousands of conifer pollen grains from the same sediment layer as browngrass seeds. Pollen age statistically matched seed age.

The researchers also used optically stimulated luminescence dating to determine the age of quartz grains within the footprint deposits. This method determines the age of an object by measuring the amount of energy trapped in it since it was buried. They found that the minimum age of the sediment layer containing the footprints is about 21,500 years.

“This study supports the chronology we established for the site in 2021 using independent methods, laboratories and approaches,” Bennett said.

A total of 61 footprints were found in a former lakeside area.

“People walked across a mosaic of wet and dry ground. This lakeside environment had mud, silt and sand,” Pigati said.

“And just like today, if someone walked through a similar environment, their footprints would be preserved if they were covered with another layer of sediment,” Springer added. .