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Paleo - human step dotting White Sands National Park in New Mexico are 23,000 to 21,000 years old , making them the oldest eff fossilized trackways leave by people in North America , a new study finds . However , not everyone agrees with the results .
The report , which used two go steady techniques to swan the trackway ’s age , is a reply to literary criticism that anearlier cogitation published in 2021by the same group used unreliable material to date stamp the step . Now , all three termination — the earlier , controversial one and the two new findings from different dating techniques — point to the trackways being 23,000 to 21,000 age old . That intend they see to around the time of the Last Glacial Maximum ( 26,500 to 19,000 years ago ) , the coldest part of thelast ice rink age .
Human footprints at White Sands in New, Mexico date to between 21,000 and 23,000 years ago.
The trackway ’s former age is a heavy business deal . antecedently , archaeologiststhought that the Clovis citizenry — known for their sharp - edged , leaf - shape stone points incur at archeological internet site across North America — were the first man to add up into the Americas around 13,000 yr ago . Only in the preceding few decennary have archeologist discovered solid grounds for the pre - Clovis , or citizenry who were in the Americas before 13,000 years ago , but many of those newly uncovered web site had rickety evidence or were only a few thousand years older than the Clovis .
The White Sands trackway is now the oldest site in North America with unmediated evidence of humans and it significantly pushes back the arriver date of the first Americans .
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An illustration that depicts different points in time at the White Sands site during the Last Glacial Maximum, when human and megafaunal lived side by side.
" When thefirst papercame out , a mountain of archaeologists hit out and told us , ' It was just a matter of time . We knew that multitude were here earlier , ' " saidJeffrey Pigati , who co - conduce the study withKathleen Springer . Both are U.S. Geological Survey inquiry geologists at the Geosciences and Environmental Change Science Center in Denver . " Now we have rock - unanimous grounds of mass here during the Last Glacial Maximum , " he said .
But in 2022 , a group of archaeologists point outin a rebuttalthat the carbon 14 date textile used in the first paper — the seeds of the aquatic plantRuppia cirrhosa — were undependable .
Scientists had found the seeds smooshed into the footprint , providing organic remainder that could be dated by study theradioactive decline of their carbon-14 . But " Ruppiais a notorious misreporter of its age,“Loren Davis , a prof of anthropology at Oregon State University who co - author the rebuttal , assure Live Science . Unlike other once - inhabit organism that inhale carbon-14 from the atmosphere , " Ruppiaprefers to get its carbon from lake water , it does n’t get it from the atmosphere . And in doing so , if there is old carbon copy being put into the groundwater , then you ’ll get previous ages on plants that are not that former , " Davis said .
A false-colored image of the footprints highlights the depth and distinction of the trackways.(Image credit: National Park Service)
In the rebuttal , Davis and his colleague suggested the White Sands chemical group use optically stimulated luminescence ( OSL ) dating , a technique that estimates how much time has passed since quartz or felspar grains were last let out to intense heating system or sunlight .
So , for the raw newspaper , publish Thursday ( Oct. 5 ) in the journalScience , the investigator did just that .
The team examined quartz grains under the footprints with OSL dating . They found that the layers with the footprints had a minimal eld of about 21,500 years previous .
White Sands National Park resource program manager, David Bustos, works in a trench at the study site.(Image credit: National Park Service)
The team also sequestrate and then radiocarbon dated three samples of earth that each contained 75,000 conifer pollen grain from the same footprint layer as theRuppiaseeds . Confer plants get their carbon-14 from the atmosphere , think of they do n’t have the same pitfalls asRuppia . The ages of around 23,000 years ago couple those of both the seeds and the lechatelierite grain . " If the seeded player ages and the pollen ages and the luminescence ages all agree , then it ’s case close , " Pigati enjoin . " We can stop reason about the ages . "
Actually , not yet , Davis said .
According to a map show where the White Sands team guide the OSL samples , " it is clear that the three OSL ages hail from sediments that are stratigraphically beneath the trackway horizons , " Davis told Live Science in an electronic mail . So it ’s potential that the crystal grains were bank first and that the footprint were deposited on top of them at a late date , possibly between 19,800 and 16,200 years ago , as one OSL sample distribution demonstrates , he said .
Human footprints infilled with white gypsum sand at the White Sands site.(Image credit: National Park Service)
" This is why it is critical that the authors keep their efforts to get OSL eld from the sediments that actually buried the footprints , " Davis enunciate . He added that it ’s possible that corrosion of older sediments at the lake basin could have caused fossil pollen to be redeposit elsewhere at a later sentence , mean that the pollen could be quondam than the footprints .
Springer and Pigati state the OSL samples were take from the same level as the footprints , while Davis stood by his interpretation of their data .
But others were impress by the findings .
Fossilized human footprints at the study site in New Mexico. During the last ice age, this area was a paleo-lake environment.(Image credit: National Park Service)
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A single human footprint at White Sands National Park.
The initial 2021 determination was " a groundbreaking result , " Higham told Live Science . " I retrieve that duplicating and reproducing those results is a trademark of the scientific method . "
