For the last hundred years, scientists argued about when people first arrived in the Americas. But in 2021, a study on human footprints found in White Sands National Park, New Mexico, changed everything. The footprints were made during the Ice Age, around 21,000 to 23,000 years ago. This is much older than what many scientists believed before, and it could change how we think humans first came to America.
The researchers have released a new study in the journal Science, which adds more evidence supporting their original dates. Summer Praetorius, a paleoceanographer at the US Geological Survey who wasn’t part of the study, said this discovery changes how we understand how people first came to America.
For years, scientists thought humans came to the Americas about 13,000 to 16,000 years ago as the Ice Age ended. But these new dates from the footprints have left archaeologists puzzled.
During the Last Glacial Maximum, about 19,000 to 26,000 years ago, huge ice sheets covered much of the Americas, making it too dangerous for humans to travel there. Yet, the footprints found in New Mexico suggest that humans might have arrived even earlier, before the route to the Americas froze completely.
Originally, the researchers dated the 61 footprints by examining the seeds of an aquatic grass called ruppia found in the sands.
Critics weren’t satisfied with this method. They pointed out that ruppia, being a plant that grows in water, might not give accurate results for radiocarbon analysis because it could have absorbed carbon atoms from the water instead of the air.
To address this concern, the researchers collected thousands of pollen grains from conifers, which are trees that grow on land, from the same layers as the ruppia seeds. This process took nearly a year. The more reliable pollen dating confirmed the original timeline of around 21,000 years.
But they didn’t stop there. They also dated the soil itself using a technique called optically stimulated luminescence. This method uses quartz grains as timekeepers because their crystalline structures accumulate energy from sunlight over time. By measuring this energy, scientists can estimate when the quartz was last exposed and deposited. The results showed that the quartz was at least 21,500 years old.
“We’ve got seed ages, we’ve got pollen ages, we’ve got luminescence ages — they all converge,” said study co-author Jeff Pigati, a geologist at the geological survey, to the NYT. “They all agree, and it’s really tough to argue against that.”
