For the past century, scientists have debated over when humans first set foot in the Americas. But in 2021, aon a set of human footprints discovered in the White Sands National Park in New Mexico blew the whole mystery wide open again.
"This opens up a whole new chapter in our understanding of the peopling of the Americas," Summer Praetorius, a paleoceanographer at the US Geological Survey who was not involved in the study,For decades, the general — yet iffy — scientific consensus was that humans populated the Americas some 13,000 years ago as the Ice Age retreated, or maybe as long as 16,000 years ago.
That wasn't good enough for critics, who pointed out that ruppia, being an aquatic plant, was an unreliable source for radiocarbon analysis, as it could have absorbed carbon atoms from the water instead of the air. But, they went one step further: dating the soil itself using a technique called optically stimulated luminescence. In a nutshell, it uses quartz grains as timekeepers, as their crystalline structures accumulate energy over time that's released by exposure to sunlight.
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