Among the sediment layers contained the stays of historical grass seeds combined with the sediment. Bennett and his colleagues radiocarbon-dated seeds from the layer just under the oldest footprints and the layer simply above the newest ones. In accordance with these 2021 outcomes, the oldest footprints had been made someday after 23,000 years in the past; the newest ones had been made someday earlier than 21,000 years in the past.
At the moment, the northern half of the continent was a number of kilometers under huge sheets of ice. The existence of 23,000-year-old footprints might solely imply that folks had been already dwelling in what’s now New Mexico earlier than the ice sheets sealed off the southern half of the continent from the remainder of the world for the subsequent few thousand years.
Historical human footprints present in situ at White Sands Nationwide Park in New Mexico.
Credit score:
Jeffrey S. Pigati et al., 2023
Different researchers had been skeptical of these outcomes, declaring that the aquatic vegetation (Ruppia cirrhosa) analyzed had been susceptible to absorbing the traditional carbon in groundwater, which might have skewed the findings and made the footprints appear older than they really had been. And the pollen samples weren’t taken from the identical sediment layers because the footprints.
So the identical workforce adopted up by radiocarbon-dating pollen sampled from the identical layers as a number of the footprints—people who weren’t too skinny for sampling. This pollen got here from pine, spruce, and fir timber, i.e., terrestrial vegetation, thereby addressing the difficulty of groundwater carbon seeping into samples. In addition they analyzed quartz grains taken from clay simply above the bottom layer of footprints utilizing a distinct technique, optically stimulated luminescence relationship. They printed these findings in 2023, which agreed with their earlier estimate.
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